GitHub dependabot supersedes CompatHelper

cf. https://discourse.julialang.org/t/psa-github-dependabot-now-supports-julia/134997

Author: emmt

.github/dependabot.yml

@@ -5,3 +5,11 @@ updates:
     directory: "/" # Location of package manifests
     schedule:
       interval: "weekly"
+  - package-ecosystem: "julia"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    # groups: # uncomment to group all julia package updates into a single PR
+    #   all-julia-packages:
+    #     patterns:
+    #       - "*"