ci: set contents read as default workflow permissions

.github/workflows/labels.yml

@@ -4,6 +4,10 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: true
 
+# https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#permissions
+permissions:
+  contents: read
+
 on:
   push:
     branches:
@@ -19,6 +23,11 @@ on:
 jobs:
   labeler:
     runs-on: ubuntu-latest
+    permissions:
+      # same as global permissions
+      contents: read
+      # required to update labels
+      issues: write
     steps:
       -
         name: Checkout