The main thing missing is that we don't serialize the supports clause,
but for actually using a `@supports (something: cool) {}` rule in CSS,
it works!
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
