Deploy the demo using Github Actions

.github/workflows/ci.yaml

@@ -1,6 +1,6 @@
 on:
   push:
-    branches: [master]
+    branches: [master, release]
   pull_request:  
 
 name: CI
@@ -106,7 +106,7 @@ jobs:
           cargo run -- -m test -v
 
   wasm:
-    name: Run wasm selenium tests
+    name: Check the WASM package and demo
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@master
@@ -134,3 +134,12 @@ jobs:
           npm install
           npm run test
         working-directory: ./wasm/demo
+      - name: Deploy demo to Github Pages
+        if: success() && github.ref == 'refs/heads/release'
+        uses: peaceiris/actions-gh-pages@v2
+        env:
+          ACTIONS_DEPLOY_KEY: ${{ secrets.ACTIONS_DEMO_DEPLOY_KEY }}
+          PUBLISH_DIR: ./wasm/demo/dist
+          EXTERNAL_REPOSITORY: RustPython/demo
+          PUBLISH_BRANCH: master
+