RPA.Dialogs close detection
This is my first time writing an Issue so please tell me if I can do anything better.

While testing Dialogs prompt I've noticed that if you close the browser the script stays halted waiting for user input, but since the browser is closed and the server keeps running the only way to break out is to force stop the script or to open again the browser in the respective served url and complete the form (which is unlikely that a user will do).
My idea to solve this is to open a new browser by checking in the function request_response this:
```
            ...
            while True:
                # if etag:
                #    headers['If-None-Match'] = etag
                try:
                    br.driver.current_window_handle  # If closed raise an exception 
                except:
                    br.open_available_browser(f"{self.server_address}/form.html")  # Open browser again
                    br.set_window_size(window_width, window_height)
                ...
```

diff --git a/packages/main/src/RPA/Dialogs.py b/packages/main/src/RPA/Dialogs.py
index 9a2ba324d..5573937e7 100644
--- a/packages/main/src/RPA/Dialogs.py
+++ b/packages/main/src/RPA/Dialogs.py
@@ -1,25 +1,23 @@
 import cgi
-from collections import OrderedDict
-from datetime import datetime
-
-# pylint: disable=no-name-in-module
-from http.server import BaseHTTPRequestHandler, HTTPServer
 import json
-from json import JSONDecodeError
 import logging
 import os
-from pathlib import Path
-
-from socketserver import ThreadingMixIn
 import shutil
 import tempfile
 import threading
 import time
-from typing import Any
+from collections import OrderedDict
+from datetime import datetime
+from http.server import (  # pylint: disable=no-name-in-module
+    BaseHTTPRequestHandler,
+    HTTPServer,
+)
+from pathlib import Path
+from socketserver import ThreadingMixIn
+from typing import Any, Dict, Optional
 from urllib.parse import unquote_plus
-import requests
-
 
+import requests
 from RPA.Browser.Selenium import Selenium
 
 try:
@@ -222,15 +220,14 @@ class Handler(BaseHTTPRequestHandler):
     def do_GET(self):
         if self.path.endswith("favicon.ico"):
             return
+
         if self.path.endswith("requestresponse"):
             if self.server.formresponse is not None:
                 self._set_response(200, "json")
                 self.wfile.write(json.dumps(self.server.formresponse).encode("utf-8"))
                 self.server.formresponse = None
-                return
             else:
                 self._set_response(304, "json")
-                return
         elif self.path.endswith(".html"):
             self._set_response(200, "html")
             if self.path == "/":
@@ -241,10 +238,8 @@ class Handler(BaseHTTPRequestHandler):
                 html = fh.read()
                 # html = bytes(html, 'utf8')
                 self.wfile.write(html)
-            return
         else:
             self._set_response(404, "html")
-            return
 
 
 class ThreadedHTTPServer(ThreadingMixIn, HTTPServer):
@@ -702,13 +697,18 @@ class Dialogs:
         self.custom_form["form"].append(element)
 
     def request_response(
-        self, formspec: str = None, window_width: int = 600, window_height: int = 1000
-    ) -> dict:
+        self,
+        formspec: str = None,
+        window_width: int = 600,
+        window_height: int = 1000,
+        timeout: Optional[int] = None,
+    ) -> Dict:
         """Start server and show form. Waits for user response.
 
         :param formspec: form json specification file, defaults to None
         :param window_width: window width in pixels, defaults to 600
         :param window_height: window height in pixels, defaults to 1000
+        :param timeout: optional time to wait for response, in seconds
         :return: form response
 
         Example:
@@ -720,47 +720,63 @@ class Dialogs:
 
         """
         self._start_attended_server()
-        if self.custom_form is None:
-            self.create_form("Requesting response")
-        if formspec:
-            formdata = open(formspec, "rb")
-        else:
-            formdata = json.dumps(self.custom_form)
-        headers = {"Accept": "application/json", "Content-Type": "application/json"}
-        requests.post(
-            f"{self.server_address}/formspec",
-            data=formdata,
-            headers=headers,
-        )
 
-        response_json = {}
         try:
-            br = Selenium()
-            br.open_available_browser(f"{self.server_address}/form.html")
-            br.set_window_size(window_width, window_height)
+            if self.custom_form is None:
+                self.create_form("Requesting response")
+
+            if formspec:
+                formdata = open(formspec, "rb")
+            else:
+                formdata = json.dumps(self.custom_form)
+
+            requests.post(
+                f"{self.server_address}/formspec",
+                data=formdata,
+                headers={
+                    "Accept": "application/json",
+                    "Content-Type": "application/json",
+                },
+            )
+
+            return self._wait_response(window_width, window_height, timeout)
+        finally:
+            self._stop_attended_server()
 
-            headers = {"Prefer": "wait=120"}
-            # etag = None
+    def _wait_response(
+        self, window_width: int, window_height: int, timeout: Optional[int]
+    ) -> Dict:
+        """Open a browser to the created form and wait for the user
+        to submit it.
+        """
+        browser = Selenium()
+
+        def is_browser_open():
+            try:
+                return bool(browser.driver.current_window_handle)
+            except Exception:  # pylint: disable=broad-except
+                return False
+
+        try:
+            browser.open_available_browser(f"{self.server_address}/form.html")
+            browser.set_window_size(window_width, window_height)
+
+            start_time = time.time()
             while True:
-                # if etag:
-                #    headers['If-None-Match'] = etag
-                headers["If-None-Match"] = "2434432243"
                 response = requests.get(
-                    f"{self.server_address}/requestresponse", headers=headers
+                    f"{self.server_address}/requestresponse",
+                    headers={"Prefer": "wait=120"},
                 )
-                # etag = response.headers.get("ETag")
+
                 if response.status_code == 200:
-                    try:
-                        response_json = response.json()
-                        break
-                    except JSONDecodeError:
-                        break
+                    return response.json()
                 elif response.status_code != 304:
-                    # back off if the server is throwing errors
-                    time.sleep(10)
-                    continue
-                time.sleep(1)
+                    response.raise_for_status()
+                elif not is_browser_open():
+                    raise RuntimeError("Browser closed by user")
+                elif timeout and time.time() > start_time + int(timeout):
+                    raise RuntimeError("No response within timeout")
+                else:
+                    time.sleep(1)
         finally:
-            br.close_browser()
-            self._stop_attended_server()
-        return response_json
+            browser.close_browser()
['packages/main/src/RPA/Dialogs.py']