ci: enable Dependabot updates for shared actions (#29)

* ci: enable Dependabot updates for shared actions

* ci: add missing version tag comment in shared actions

Author: MattIPv4

.github/dependabot.yml

@@ -1,7 +1,9 @@
 version: 2
 updates:
   - package-ecosystem: "github-actions"
-    directory: "/"
+    directories:
+      - /
+      - /actions/*
     schedule:
       interval: "monthly"
     cooldown:

actions/notify-on-push/action.yml

@@ -10,7 +10,7 @@ runs:
   using: "composite"
   steps:
     - name: Slack Notification
-      uses: rtCamp/action-slack-notify@e31e87e03dd19038e411e38ae27cbad084a90661
+      uses: rtCamp/action-slack-notify@e31e87e03dd19038e411e38ae27cbad084a90661 # v2.3.3
       env:
         SLACK_COLOR: "#DE512A"
         SLACK_ICON: https://github.com/nodejs.png?size=48