workflows: update pr-auditor workflow (#139)

Author: bobheadxi

.github/workflows/pr-auditor.yml

@@ -1,10 +1,11 @@
+# See https://docs.sourcegraph.com/dev/background-information/ci#pr-auditor
 name: pr-auditor
 on:
-  pull_request:
-    types: [ closed, edited, opened ]
+  pull_request_target:
+    types: [ closed, edited, opened, synchronize, ready_for_review ]
 
 jobs:
-  run:
+  check-pr:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2