Set permissions for GitHub actions

Restrict the GitHub token permissions only to the required ones; this
way, even if the attackers will succeed in compromising your workflow,
they won’t be able to do much.

- Included permissions for the action.

https://github.com/ossf/scorecard/blob/main/docs/checks.md#token-permissions

https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#permissions

https://docs.github.com/en/actions/using-jobs/assigning-permissions-to-jobs

Keeping your GitHub Actions and workflows secure Part 1: Preventing pwn requests
https://securitylab.github.com/research/github-actions-preventing-pwn-requests/

Signed-off-by: naveen <172697+naveensrinivasan@users.noreply.github.com>

Closes gh-11367

.github/workflows/pr-build-workflow.yml

@@ -5,6 +5,9 @@ on: pull_request
 env:
   RUN_JOBS: ${{ github.repository == 'spring-projects/spring-security' }}
 
+permissions:
+  contents: read
+
 jobs:
   build:
     name: Build