The react-styles class maps generator should use a CSS parser instead of custom regex

[mturley]

Describe the issue. What is the expected and unexpected behavior?

See https://github.com/patternfly/patternfly-react/pull/4066/files#r407659068. We are using a custom regular expression to extract the class names from CSS strings, we should instead use a parser library so we don't have to worry about reliability and maintenance of that regex.

[stale]

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