Move pre-commit gihub workflow to dependabot.

Author: hyperboloid

.github/dependabot.yml

@@ -7,3 +7,9 @@ updates:
       # Check for updates on the first Sunday of every month, 8PM UTC
       interval: "cron"
       cronjob: "0 20 * * sun#1"
+  - package-ecosystem: "pre-commit"
+    directory: "/"
+    schedule:
+      # Check for updates on the first Sunday of every month, 8PM UTC
+      interval: "cron"
+      cronjob: "0 20 * * sun#1"