chore: enable dependabot (#15)

.github/dependabot.yml

@@ -0,0 +1,13 @@
+version: 2
+updates:
+  - package-ecosystem: "pip"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "wednesday"
+      time: "09:00"
+    # Disable version updates, keep security updates only
+    open-pull-requests-limit: 0
+    commit-message:
+      # Prefix all commit messages with "chore: "
+      prefix: "chore"