This PR fixes an issue where some special characters (with an actual
meaning CSS) were used inside of the `url(…)` function, would result in
incorrectly parsed CSS.
For example, when we encounter a `{`, then we would start a new "block"
for nesting purposes. If we encounter an `}`, then the block would end.
If we encounter a `;`, then that would be the end of a declaration.
All of that is true, unless we are in a `url(…)` function. In that case,
we should ignore all of those characters and treat them as part of the
URL.
This is only an issue because:
1. We are allowed to use these characters in URLs.
2. We can write an url inside `url(…)` without quotes. With quotes, this
would not be an issue.
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Co-authored-by: Philipp Spiess <hello@philippspiess.com>
4e164107dd