[Discovery] Custom Fonts: support `woff2`

Feature Description

Currently we’re using opentype.js for getting the information about the font from the font file URL, however, this library doesn’t support woff2.

There are some libraries that support woff2: opentype and fontkit. Both of these mention also having browser support, however, apparently both modules require fs module by default in various places which causes the editor to crash.

There are a few GitHub issues in the repos of both modules stating the concern of not being able to use these in the browser with a bunch of suggested solutions for webpack, however, many of those didn’t work when trying / were quite outdated and caused more issues.

We should take another look to figure out a way to support woff2.

Alternatives Considered

Additional Context

[miina]

Let’s not close this issue before we actually decide what to do and if we need a follow-up implementation issue or not 😃 Moving to Review instead.

[merapi]

Bottom line: most of those libraries aren’t written with the browser in mind and would require some modifications to work either by switching out the dependencies (forking or patching with upstream PRs?) or implementing woff2 support.

We don’t need most of the features that libraries like fontkit offer (consider bundle size), we don’t need writing to font files (includes Brotli compression), we just need to read some of the font metrics. So it makes some sense to develop our tailor-made solution, but it will take time (days). On the other hand, woff2 fonts can be easily converted to woff1 by the end-user.

Depending on the demand, we should decide what to do next.