fix branch reference

Author: gregsdennis

.github/workflows/publish-site.yml

@@ -25,7 +25,7 @@ jobs:
   publish:
     name: pack & publish
     runs-on: ubuntu-latest
-    if: env.BRANCH == 'main'
+    if: github.ref == 'refs/heads/main'
     steps:
       - uses: actions/checkout@v3
       - name: restore submodules