only allow push in main to deploy to gh-page (#146)

this prevents push in other branches for ex dev to deploy to gh-page

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Co-authored-by: Huong Pham <huong.pham@zubax.com>

Author: songmeo

.github/workflows/build.yml

@@ -49,6 +49,7 @@ jobs:
     environment:
       name: github-pages
     needs: build
+    if: github.ref == 'refs/heads/main'
     runs-on: ubuntu-latest
     permissions:
       pages: write