ci: [StepSecurity] Apply security best practices (#884)

Signed-off-by: StepSecurity Bot <bot@stepsecurity.io>
Co-authored-by: stepsecurity-app[bot] <188008098+stepsecurity-app[bot]@users.noreply.github.com>

Author: stepsecurity-app[bot]

.github/workflows/size_labels.yml

@@ -2,13 +2,21 @@ name: "Pull request size labels"
 
 on: [pull_request]
 
+permissions:
+  contents: read
+
 jobs:
   labeler:
     permissions:
       pull-requests: write
       contents: read
     runs-on: ubuntu-latest
     steps:
+      - name: Harden the runner (Audit all outbound calls)
+        uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
+        with:
+          egress-policy: audit
+
       - name: Size Labeler
         uses: codelytv/pr-size-labeler@095a41fca88b8764fd9e008ad269bcdb82bb38b9
         with: