Simplify the version bump process. ### Description

Simplify the version bump process.

- Use substitution hook in docs to update CDN URL.
  - In `dev` or `prerelease` versions, it will point to `dev` url
  - In `stable` versions, it will point it `vX.Y.Z` url
- Introduce a version bump script `tools/bump_version.py`.


~- Use `bump2version` to bump Python versions (continuing from #2460)~
~- Use `npm version` to bump JS versions~
~- Update `run_docker` script to use latest deployed pre-built docker image when `--pre-built` option is specified.~

### Checklists

- [x] Add new / update outdated documentation

package:
  name: soupsieve
  version: 2.3.1
source:
  sha256: 1a3cca2617c6b38c0343ed661b1fa5de5637f257d4fe22bd9f1338010a1efefb
  url: https://files.pythonhosted.org/packages/72/a6/fd01694427f1c3fcadfdc5f1de901b813b9ac756f0806ef470cfed1de281/soupsieve-2.3.1-py3-none-any.whl
test:
  imports:
    - soupsieve

package:
  name: soupsieve
  version: 2.3.1
source:
  sha256: 1a3cca2617c6b38c0343ed661b1fa5de5637f257d4fe22bd9f1338010a1efefb
  url: https://files.pythonhosted.org/packages/72/a6/fd01694427f1c3fcadfdc5f1de901b813b9ac756f0806ef470cfed1de281/soupsieve-2.3.1-py3-none-any.whl
test:
  imports:
    - soupsieve
