Add syntax highlighting for Python match-case statements

[Cheesecake2960]

This adds support for Python 3.10's match/case syntax.

Changes:

• Added match and case to the list of Python keywords in the lexer
• Updated the visual sample for Python syntax highlighting (in spec/visual/samples/python)

This is part of Python 3.10's structural pattern matching feature.

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This is my first contribution to Rouge. I'm happy to receive any feedback!

[tancnle]

Duplicate of https://github.com/rouge-ruby/rouge/pull/1981.