[WIP] Feature comments

*Don't merge yet.* 

Progress: https://github.com/BiteKollektiv/fairnopoly/issues?milestone=2&state=open

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This adds commenting functionality to libraries. Users are able to view and create comments below each library. 

I'm mainly looking for feedback on the code with this early PR.

:heart:
Prefer double-quoted strings unless you need single quotes to avoid extra backslashes for escaping.