Add local font selection for supported browsers and desktop

Chromium browsers recently got the ability to browse local fonts. We should provide a way to choose between the Google Fonts list and local fonts, but gray that out with an explanation telling the user to use a Chromium browser for unsupported browsers.

- https://developer.mozilla.org/en-US/docs/Web/API/Local_Font_Access_API
- https://developer.chrome.com/en/blog/how-boxysvg-uses-the-local-font-access-api/
- https://developer.chrome.com/articles/local-fonts/

Related: #2125

Start by reading the Local Font Access API references linked in the issue and the discussion in related issue #2125. No source file, test, or entry point is identified in the payload; done means offering Google Fonts or local-font selection where supported and disabling it with an explanation in unsupported browsers.

索引モデルが issue の本文から書いたものです。