Improve documentation

[albe]

Currently the documentation is relatively unstructured and misses proper explanation/listing of all available options. Also some more practical usage examples with explanations would do good.

[albe]

Check out https://docusaurus.io/docs/en/next/tutorial-setup for documentation

[albe]

Decided for readthedocs.io now using mkdocs renderer. Docs are written as md inside the docs folder.

https://node-event-storage.readthedocs.io/en/latest/

See https://www.mkdocs.org/user-guide/writing-your-docs/ for more information, the configuration is inside the mkdocs.yml in the root.