Composer Audit Workflow: Run on pull requests (#9)

Author: tangrufus

.github/workflows/composer-audit.yml

@@ -4,6 +4,12 @@ on:
   workflow_dispatch:
   schedule:
     - cron: '23 3 * * 1' # Weekly on Monday
+  pull_request:
+    branches:
+      - main
+    paths:
+      - .github/workflows/composer-audit.yml
+      - composer.*
   push:
     branches:
       - main