Adds publish of docs for non-main-branch

This way we can test it out/share

.github/workflows/docs.yml

@@ -6,7 +6,7 @@ on:
       - main # Triggers the workflow on push events to the main branch
   pull_request:
     # Triggers the workflow on pull request events for any branch
-    types: [ opened, synchronize, reopened ]
+    types: [opened, synchronize, reopened]
 
 permissions:
   contents: write
@@ -23,12 +23,14 @@ jobs:
       - name: Sphinx build
         run: |
           sphinx-build docs -b dirhtml _build
-          echo "burr.dagworks.io" > _build/CNAME # keep the cname file which this clobbers -- todo, unhardcode
+      - name: Set CNAME for main branch
+        if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }}
+        run: echo "burr.dagworks.io" > _build/CNAME
       - name: Deploy to GitHub Pages
         uses: peaceiris/actions-gh-pages@v3
-        if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }}
         with:
-          publish_branch: gh-pages
+          publish_branch: |
+            ${{ github.event_name == 'pull_request' && 'pr-' + github.event.pull_request.number || 'gh-pages' }}
           github_token: ${{ secrets.GITHUB_TOKEN }}
           publish_dir: _build/
           force_orphan: true