ci: ignore errors in greetings workflow

See: actions/first-interaction#101

.github/workflows/greetings.yml

@@ -10,6 +10,7 @@ jobs:
       pull-requests: write
     steps:
     - uses: actions/first-interaction@v1
+      continue-on-error: true
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}
         issue-message: 'Hello there, thanks for opening your first issue. We welcome you to the community!'