ci: prevent the jobs for running on an action for fork

See details in actions/github-script#42

Author: derevnjuk

.github/workflows/build.yml

@@ -104,6 +104,7 @@ jobs:
         run: yarn build
 
   benchmarks:
+    if: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name == github.repository }}
     runs-on: ubuntu-latest
     strategy:
       matrix: