Tokenize subclass list names in tree-sitter grammar

Requirements

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All new code requires tests to ensure against regressions

Description of the Change

This PR tokenizes the names of subclasses listed within class definitions, for Python files matched by the tree-sitter grammar.

Before:

After:

Alternate Designs

I don't know if the Atom team desires to tokenize these subclass names differently; I figured entity.other.inherited-class was the most appropriate scope, as it's based on the same scope from the first-mate grammar.

Benefits

Syntax highlighting that is more familiar to longtime users of the Python first-mate grammar.

Possible Drawbacks

Perhaps some might prefer different colors be used for the subclass names, though I personally like them.

Applicable Issues

N/A

atom / language-python