Add dependabot config (#3)

* Add dependabot config

Automatically opens a PR if there are new releases of GitHub Actions or Dockerfile base image

* Update dependabot.yml

---------

Co-authored-by: Christian Clauss <[email protected]>

Author: fhemberger

.github/dependabot.yml

@@ -0,0 +1,18 @@
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    groups:
+      github-actions:
+        patterns:
+          - "*"  # Group all Actions updates into a single larger pull request
+    schedule:
+      interval: weekly
+  - package-ecosystem: docker
+    directory: /
+    groups:
+      docker:
+        patterns:
+          - "*"  # Group all Docker updates into a single larger pull request
+    schedule:
+      interval: weekly