Add Dependabot for GitHub Actions

.github/dependabot.yml

@@ -0,0 +1,28 @@
+# Copyright 2026 Open Reaction Database Project Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Actions in .github/workflows are pinned to commit SHAs. Dependabot rewrites
+# both the SHA and its trailing version comment, which is what keeps a pinned
+# workflow from freezing on whatever was current the day it was written.
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: monthly
+    groups:
+      # One pull request per month for all actions rather than one per action.
+      actions:
+        patterns:
+          - "*"