chore: Dependabot to handle monorepo

With the pnpm change to have a monorepo structure - to allow for better
usage of the Makefile and whatnot - we need to update Dependabot to
tell it this is a monorepo of sorts.

This also deletes the pnpm-lock that is in frontend/ as it is no longer
being used

.github/dependabot.yml

@@ -0,0 +1,9 @@
+version: 2
+updates:
+  - package-ecosystem: "npm"
+    directory: "/"
+    schedule:
+      interval: "daily"
+      time: "09:00"
+      timezone: "Europe/Berlin"
+    versioning-strategy: increase