Add Dependabot for GitHub Actions updates

Automatically keep GitHub Actions versions up to date
with weekly update checks.

Assisted-by: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Stephane Bouchet <sbouchet@redhat.com>

Author: sbouchet

.github/dependabot.yml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"