This PR adds a small note to the README for matches to warn the user that they can be vulnerable to ReDoS (Regular Expression Denial of Service) attacks if they let users define their own pattern.

To reduce the amount of PRs needed, I have also prepared a new release in this PR. Unlike the other PRs, we should not squash and merge this PR so we can keep commits separate.

Checklist

• PR contains only changes related; no stray files, etc.
• README updated (where applicable)
• Tests written (where applicable)
• References provided in PR (where applicable)