typst css: don't wear out the "unknown font family" warning

[gordonwoodhull]

It's very helpful that Typst now warns about unknown fonts as of 1.12. However, it can be alarming / unhelpful for our use case.

In particular, it is a very different model from CSS font-family lists, which silently ignore missing fonts.

We can list what fonts are available for Typst with

quarto typst fonts

It takes about 5s on my Mac to list ~500 system fonts, but only 0.17s to list the 4 built-in fonts with

quarto typst fonts --ignore-system-fonts

So maybe with judicious use of --font-path and --ignore-system-paths we could quickly get a list of available fonts and then filter out the unavailable fonts when translating from CSS font-family lists to Typst font family lists.

We are already transforming these lists e.g #12542 font family lists, #11918 generic font families.

Related Typst issue: typst/typst#6010

[cderv]

It takes about 5s on my Mac to list ~500 system fonts, but only 0.17s to list the 4 built-in fonts with

FWIW if I call this on windows it is less that 1s for both: 0.865s and 0.553s . So acceptable

[cscheid]

We can also consider caching the result of these calls.