Add automation script to generate mkdocstrings files

[seratch]

This pull request adds a new script for docs, which generates missing ref/**/*.md files. The script can be executed when you run make build-docs command. The script does not do:

• overwrite the existing ones
• create files for _XXX.py and __init__.py

Note that the title part is generated like tool_context to Tool Context. openai_provider will be Openai Provider, so some of them needs a little manual work to adjust.

The direct need is to add tool_context.md for #1043 but it should be useful for future maintenance.

[rm-openai]

Hey @seratch the code looks totally fine but I actually don't get why we need this? Why can't the files just be hand-written, takes like 5 seconds lol