message: Preserve co-authors in `clear-pr-merge-commit-message`
  It was case-sensitive
diff: @@ -7,7 +7,7 @@ import onPrMergePanelOpen from '../github-events/on-pr-merge-panel-open';
  function init(): void {
  const messageField = select<HTMLTextAreaElement>('#merge_message_field')!;
  - const coAuthorsMatches = messageField.value.matchAll(/Co-Authored-By: [^\n]+/g);
  + const coAuthorsMatches = messageField.value.matchAll(/co-authored-by: [^\n]+/gi);
  const coAuthors = [...new Set([...coAuthorsMatches].flat())]; // Deduplicate Co-Authors
  messageField.value = coAuthors.join('\n');
  