Simplify adding new node docs

[Durman]

Addressed problem description

It seems redundant to keep list of node documentation file names - https://www.sphinx-doc.org/en/master/usage/restructuredtext/directives.html#directive-toctree

Now it's enough to add node_name.rst file to appropriate folder in the docs without adding the file name into a index.rst file.

Preflight checklist

• Code changes complete.
• Documentation for users complete (or not required, if user never sees these changes).
• Ready for merge.