Fix PR workflows

.github/workflows/pr.yml

@@ -1,10 +1,6 @@
 name: PR Workflow
 
-on:
-  pull_request:
-    types: [opened, synchronize, ready_for_review, edited, closed]
-    branches:
-      - master
+on: pull_request_target
 
 jobs:
   release:
@@ -21,9 +17,9 @@ jobs:
         uses: actions/cache@v2
         with:
           path: /tmp/.buildx-cache
-          key: ${{ runner.os }}-buildx-${{ github.sha }}
+          key: ${{ runner.os }}-buildx-prs-${{ github.sha }}
           restore-keys: |
-            ${{ runner.os }}-buildx-
+            ${{ runner.os }}-buildx-prs-
 
       - name: Login to DockerHub
         uses: docker/login-action@v1