build: harden build_doc.yml permissions

Signed-off-by: Alex <aleksandrosansan@gmail.com>

.github/workflows/build_doc.yml

@@ -4,9 +4,16 @@ on:
   issue_comment:
       types: [created]
 
+permissions:
+  contents: read # to fetch code (actions/checkout)
+
 jobs:
   build:
 
+    permissions:
+      contents: read # to fetch code (actions/checkout)
+      issues: write # to create comment
+
     runs-on: ubuntu-latest
     steps:
       - uses: actions/github-script@v6