This way, we can show the plus and minus buttons on screens, while voice
control will read off actual words "Collapse" and "Expand" instead of reading
"open brace minus close brace" and "open brace plus close brace".
Part of #87059
rustdoc: add optional woff2 versions of Source Serif and Source Code
This provides woff2 versions of Source Serif and Source Code similar to how #82545 provides woff2 versions of Fira Sans. The total byte count for the six files (three for each font family) is reduced by 25% from 476 KiB to 358 KiB.
Replaces a format!() call in layout::render with a template
expansion. Introduces a `templates` field in SharedContext so parts
of rustdoc can share pre-rendered templates.
This currently builds in a copy of the single template available, like
with static files. However, future work can make this live-loadable with
a perma-unstable flag, to make rustdoc developers' work easier.
Avoid CJK legacy fonts in Windows
As metioned in #84035, the default serif CJK font in Windows is meh-looking.
To avoid this, we should use sans-serif font or provide CJK glyph supported font in `rustdoc.css`.
Update Source Code Pro and include italics
Fixes#65502.
A few notes:
* As stated in #65502, this does increase the download size.
* Since this PR changes the font set, I think docs.rs would have to be updated if this PR is merged.
* The fonts have a double extension (.ttf.woff); this is to keep the names consistent with the upstream font release which does that to distinguish these from the .otf.woff files ([Source Code Pro otf renders poorly on older Windows system apps](https://github.com/adobe-fonts/source-code-pro/issues/25#issuecomment-9019600)).
