feat: Allow validation workflow to run on forks

.github/workflows/validate-lockfile.yml

@@ -1,7 +1,7 @@
 name: Validate pnpm-lock.yaml
 
 on:
-  pull_request:
+  pull_request_target:
     paths:
       - 'pnpm-lock.yaml'
       - '**/package.json'
@@ -15,6 +15,8 @@ jobs:
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
+          ref: ${{ github.event.pull_request.head.sha }}
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
 
       - name: Set up Node.js
         uses: actions/setup-node@v4