23.03.0 release

This is the next release that is live on search.marginalia.nu as of March 27.

Improvements

• A massive code restructuring effort [code-only].
• Fixed nasty crawler bug that caused it to immediately fail on some websites
• Fixed several nasty keyword extraction bugs that prevented
• More consistent stripping of diacretics "asciification"
• Better result ranking with regards to multiple keywords
• Support for plain text files reintroduced
• Many small GUI fixes and quality-of-life improvements