chore: Configure Dependabot to update actions

Author: smockle

.github/dependabot.yml

@@ -15,3 +15,19 @@ updates:
     directory: "/.github/actions/fix"
     schedule:
       interval: "weekly"
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+  - package-ecosystem: "github-actions"
+    directory: "/.github/actions/gh-cache/cache"
+    schedule:
+      interval: "weekly"
+  - package-ecosystem: "github-actions"
+    directory: "/.github/actions/gh-cache/restore"
+    schedule:
+      interval: "weekly"
+  - package-ecosystem: "github-actions"
+    directory: "/.github/actions/gh-cache/save"
+    schedule:
+      interval: "weekly"