Documentation: Implement automatic spell checking

[activus-d]

There is a need to implement automatic spell check to reduce manual proofreading and catch typos before opening a pull request. This will improve the quality and consistency of the documentation.

We can use the sphinxcontrib.spelling extension. The spell check should run locally after executing the make run command.

[activus-d]

We won’t use the sphinxcontrib.spelling extension. Although it works well for reStructuredText, it causes issues during dependency setup. The extension depends on pyenchant, which requires the enchant C library.

The main issue is the enchant C library, especially on macOS and Windows. Users often need to set the library path manually using environment variables, which appears to be a common issue with the library.

I’ve tried pyspelling instead and it's great for our use case. It’s simple and easy to configure. Since it doesn’t support .rst files directly, we would be running the spelling check on the built HTML files.

[Stormheg]

I think we can close this now that #77 is merged 🎉