Fix the issue with parsing @keyframes.

Also add a test case and update some test files to capture the issue with @keyframes parsing.

This fixes #7494 and #8463.
Nice fix. This might be needed somewhere else, so this cold be a function called something like `skipToClosingBracket(char)`. It only needs to handle braces for now, but it would be easy to add support for other brackets, if necessary.