docs(nx-dev): add missing permissions to GH CI example (#21137)

docs/shared/monorepo-ci-github-actions.md

@@ -15,6 +15,11 @@ on:
       - main
   pull_request:
 
+# Needed for nx-set-shas when run on the main branch
+permissions:
+  actions: read
+  contents: read
+
 jobs:
   main:
     runs-on: ubuntu-latest
@@ -59,6 +64,11 @@ on:
       - main
   pull_request:
 
+# Needed for nx-set-shas when run on the main branch
+permissions:
+  actions: read
+  contents: read
+
 jobs:
   main:
     name: Nx Cloud - Main Job
@@ -113,6 +123,11 @@ on:
       - main
   pull_request:
 
+# Needed for nx-set-shas when run on the main branch
+permissions:
+  actions: read
+  contents: read
+
 env:
   NX_CLOUD_DISTRIBUTED_EXECUTION: true # this enables DTE
   NX_CLOUD_DISTRIBUTED_EXECUTION_AGENT_COUNT: 3 # expected number of agents