Add dependabot config to update github actions as needed

Signed-off-by: Dave Thaler <[email protected]>

.github/dependabot.yml

@@ -0,0 +1,17 @@
+# For documentation on the format of this file, see
+# https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
+---
+version: 2
+updates:
+
+  - package-ecosystem: "github-actions"
+    # Workflow files stored in the
+    # default location of `.github/workflows`
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "saturday"
+    groups:
+      actions:
+        patterns:
+          - "*"