Add permissions section for pull request and content access in auto-assign Copilot reviewer workflow

Author: jongio

.github/workflows/auto-assign-copilot-reviewer.yml

@@ -4,6 +4,10 @@ on:
   pull_request:
     types: [opened, reopened, ready_for_review]
 
+permissions:
+  pull-requests: write
+  contents: read
+
 jobs:
   assign-copilot:
     runs-on: ubuntu-latest