Create dependabot.yml (#328)

Signed-off-by: Andreas Fehlner <fehlner@arcor.de>

Author: andife

.github/dependabot.yml

@@ -0,0 +1,18 @@
+# Copyright (c) ONNX Project Contributors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    # Workflow files stored in the
+    # default location of `.github/workflows`
+    directory: "/"
+    schedule:
+      interval: "monthly"
+    cooldown:
+      default-days: 7
+    open-pull-requests-limit: 20
+    labels:
+      - "github_actions"
+      - "run release CIs"