ci: Allow lint workflow to be manually triggered

Without this a different event must occur to trigger the workflow, which is inconvenient for automated PRs.

.github/workflows/linting.yml

@@ -1,10 +1,10 @@
 name: Lint
 
 on:
+  # A workflow that creates a PR will not trigger this workflow,
+  # Providing a manual trigger as a workaround
+  workflow_dispatch:
   pull_request:
-    paths-ignore:
-      # Managed by workflow: contributors.yml
-      - CONTRIBUTORS.md
   push:
     branches: [ master ]