Basically a complete overhaul of the plug

[MrMugame]

The main changes are

• Version-bumped KaTeX, SilverBullet API and removed the handlebars and yaml (?), which were in the import_map
• Bundled KaTeX JS into the Plug and not load it from the CDN every the time the iframe is generated. This saves a little on the browser resources.
• Added settings, which are checked using valibot. That adds a new dependency, but I think a reasonable one. Not using a validation framework would make the code very error prone and more complex. Valibot is only ~2KiB and super easy to understand. The specific settings are documented in the README
• Some weird logic to avoid white flashing and height jumping during load
• Updated the README

[zefhemel]

Seems to work as advertised based on some (limited) testing. Thanks!