Added dependabot for GitHub Actions

How about using dependabot in this way? When this works, a pull request is created as follows: - ruby/bigdecimal#242 It was created with reference to the following: - ruby/csv#265
exiftool-rb · Oct 3, 2023 · 8fc63fa · 8fc63fa
1 parent a9030ad
commit 8fc63fa
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/.github/dependabot.yml b/.github/dependabot.yml
@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"