Define top level read permission for docs-build-push (#769)

Author: jackbhickey

.github/workflows/docs-build-push.yml

@@ -18,6 +18,9 @@ on:
     paths:
       - site/**
 
+permissions:
+  contents: read
+
 jobs:
   call-docs-build-push:
     uses: nginxinc/docs-actions/.github/workflows/docs-build-push.yml@03a9a3808fcb77cd0c19d7fa5d59b25565dd1d6d # v1.0.2