ci: add minimum GitHub token permissions for workflows (webpack#1470)

Author: ashishkurmi

.github/workflows/cancel.yml

@@ -1,7 +1,12 @@
 name: Cancel
 on: [push]
+permissions:
+  contents: read
+
 jobs:
   cancel:
+    permissions:
+      actions: write # for styfle/cancel-workflow-action to cancel/stop running workflows
     name: Cancel Previous Runs
     runs-on: ubuntu-latest
     timeout-minutes: 3