Support for WOFF2 compressed font files

## What problem does this solve or what need does it fill?

[WOFF and WOFF2](https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_fonts/WOFF) are web-based font formats that offer advanced compression of underlying TTF/OTF font data. Given that bevy applications can also target the web, the same kinds of download size concerns apply here, so it would be nice to support this format.

## What solution would you like?

Ideally the `FontLoader` would transparently support `.woff2` files and do whatever is necessary to decompress them during load time.

## What alternative(s) have you considered?

Use a general-purpose compression mechanism instead. zstd's higher compression settings are almost able to reach WOFF2 file sizes, but not quite.

Start at the FontLoader entry point and trace how existing TTF/OTF font files are loaded. Determine the decompression and platform support needed for .woff2 files, then verify that a Bevy application can load them successfully on web targets.

Written by the indexing model from the issue text.