chore: add contributors.yml

Author: JoshuaKGoldberg

.github/workflows/contributors.yml

@@ -0,0 +1,15 @@
+jobs:
+  contributors:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: JoshuaKGoldberg/[email protected]
+      - uses: stefanzweifel/git-auto-commit-action@v4
+        with:
+          commit_message: "Fill in all-contributors"
+
+name: Contributors
+
+on:
+  push:
+    branches:
+      - main