fix: [StepSecurity] ci: Harden GitHub Actions (#2907)

Signed-off-by: StepSecurity Bot <[email protected]>
Co-authored-by: Utkarsh Umesan Pillai <[email protected]>

Author: step-security-bot

.github/workflows/benchmark.yml

@@ -13,6 +13,9 @@ on:
     branches:
       - main
 name: benchmark pull requests
+permissions:
+  contents: read
+
 jobs:
   runBenchmark:
     name: run benchmark

.github/workflows/markdown-link-check.yml

@@ -8,6 +8,9 @@ on:
     paths:
       - '**/*.md'
 
+permissions:
+  contents: read
+
 jobs:
   markdown-link-check:
     runs-on: ubuntu-latest