[docs] use `versionadded`, `versionchanged` and `deprecated` directive
📚 Documentation
Use .. versionadded::, .. versionchanged:: and .. deprecated:: directive, so that user knows which features are added / changed / deprecated in which version and they can navigate the docs easily without changing the docs from version to version.
Ref: https://www.sphinx-doc.org/en/master/usage/restructuredtext/directives.html#directive-versionadded
One thing to aware is that Lightning releases every week and every week contains a bug fix. So after 2 minor releases, we can have at most 8 .. versionchanged:: which can bloat the docs.
What do you think?