It flags the regexes whose search is quadratic in the input length, like
the autolinker and XFA-path ones fixed recently.
The three existing offenders: `\s*` matched the CSS indentation but also
the line terminators that make `^` match with the `m` flag (the
preprocessed CSS is unchanged), `(\d+)` made every digit of a number a
candidate start position, and `/T.*$/` could fail on the `$` and
backtrack since `.` doesn't match a line terminator.
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