Enable dependabot for both GH actions and Go (#119)

With the changes done in #118 we want to enable automatic workflow
version updates.

.github/dependabot.yaml

@@ -0,0 +1,17 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    open-pull-requests-limit: 15
+  - package-ecosystem: "gomod"
+    directories:
+      - "/"
+    schedule:
+      interval: "daily"
+    open-pull-requests-limit: 15
+    groups:
+      k8s:
+        patterns:
+          - "k8s.io/*"