ci: GitHub workflows security hardening (#6743)

Author: sashashura

.github/workflows/ci.yml

@@ -6,6 +6,10 @@ on:
   pull_request:
     branches:
       - main
+
+permissions:
+  contents: read # to fetch code (actions/checkout)
+
 jobs:
   unit-test:
     runs-on: ubuntu-latest

.github/workflows/release-tag.yml

@@ -5,8 +5,12 @@ on:
 
 name: Create Release
 
+permissions: {}
 jobs:
   build:
+    permissions:
+      contents: write # to create release (yyx990803/release-tag)
+
     name: Create Release
     runs-on: ubuntu-latest
     steps: