Action fails when a keyword is set to an invalid regex expression

[iliapolo]

This commit made it so that keywords are treated as regular expressions, as opposed to literal strings before.

This resulted in our action failing with:

issue content: chore: fix unmatched parenthesis in issue-label-assign
Error: Invalid regular expression: /(?!-)\bevent-bridge)\b(?!-)/: Unmatched ')'

While its true we had missing parentheses in our configuration, i'm not sure this was the intended behavior, as the commit title seems to suggest it was just meant validate the keyword itself was surrounded with alphanumeric characters.

If it is meant as a regular expression, I suggest to add this to the documentation, and mention this is actually a breaking change. If not, the keyword needs to be properly escaped.