This should cause no user-facing changes.
Now the per-language overrides are expressed as pure data and styling
happens in a single file. We can clearly see the types of
customization that have been made so far.
The CSS styling has also been enhanced, it can now be customized by
setting the CSS variables alone.
Bug: T370027
Change-Id: I2a1bf0365ac0c40991a4fe3f9a2c05dba8b7510c
