Export PATH and ERRNO_CODES from Emscripten. ### Description

Fixes #2577 by exporting `PATH` and `ERRNO_CODES` from Emscripten

### Checklists

- [x] Add a [CHANGELOG](https://github.com/pyodide/pyodide/blob/main/docs/project/changelog.md) entry
- [x] Add / update tests
- [x] Add new / update outdated documentation

(packages-in-pyodide)=

# Packages built in Pyodide

The list of prebuilt Python packages in the current version of Pyodide.
These packages can be loaded through {any}`pyodide.loadPackage` or {any}`micropip.install`.
See {ref}`loading_packages` for information about loading packages.
Note that in addition to this list, pure Python packages with wheels can be loaded
directly from PyPI with {any}`micropip.install`.

```{eval-rst}
.. pyodide-package-list :: packages
```

(packages-in-pyodide)=

# Packages built in Pyodide

The list of prebuilt Python packages in the current version of Pyodide.
These packages can be loaded through {any}`pyodide.loadPackage` or {any}`micropip.install`.
See {ref}`loading_packages` for information about loading packages.
Note that in addition to this list, pure Python packages with wheels can be loaded
directly from PyPI with {any}`micropip.install`.

```{eval-rst}
.. pyodide-package-list :: packages
```
