Include GitHub Actions in Dependabot version updates

Closes gh-2685

Author: marcusdacoregio

.github/dependabot.yml

@@ -61,3 +61,29 @@ updates:
         update-types: [ "version-update:semver-major" ]
       - dependency-name: "*"
         update-types: [ "version-update:semver-major", "version-update:semver-minor" ]
+
+  #    GitHub Actions
+
+  - package-ecosystem: github-actions
+    target-branch: "main"
+    milestone: 154
+    directory: "/"
+    schedule:
+      interval: weekly
+  - package-ecosystem: github-actions
+    target-branch: "3.2.x"
+    milestone: 152
+    directory: "/"
+    schedule:
+      interval: weekly
+  - package-ecosystem: github-actions
+    target-branch: "3.1.x"
+    milestone: 151
+    directory: "/"
+    schedule:
+      interval: weekly
+  - package-ecosystem: github-actions
+    target-branch: "docs-build"
+    directory: "/"
+    schedule:
+      interval: weekly