Dependabot: monitor 5.0 branch as well

Author: robsdedude

.github/dependabot.yml

@@ -1,6 +1,8 @@
 version: 2
 updates:
-  - package-ecosystem: "github-actions"
+  - &githubactions
+    package-ecosystem: "github-actions"
+    target-branch: "6.x"
     directory: "/"
     schedule:
       interval: daily
@@ -11,3 +13,5 @@ updates:
       - "no changelog"
     assignees:
       - "robsdedude"
+  - <<: *&gh-actions
+    target-branch: "5.0"