add custom domain CNAME for GH Pages publish (#29)

.github/workflows/deploy.yaml

@@ -27,11 +27,12 @@ jobs:
       # Popular action to deploy to GitHub Pages:
       # Docs: https://github.com/peaceiris/actions-gh-pages#%EF%B8%8F-docusaurus
       - name: Deploy to GitHub Pages
-        uses: peaceiris/actions-gh-pages@v3
+        uses: peaceiris/actions-gh-pages@v4
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           # Build output to publish to the `gh-pages` branch:
           publish_dir: ./build
+          cname: docs.hauler.dev
           # The following lines assign commit authorship to the official
           # GH-Actions bot for deploys to `gh-pages` branch:
           # https://github.com/actions/checkout/issues/13#issuecomment-724415212