chore: deploy demo action

* create deploy demo script
* action trigger guide added

.github/workflows/demoDeploy.yml

@@ -0,0 +1,24 @@
+
+name: Deploy to demo
+
+on:
+  repository_dispatch:
+    types: deploy-to-demo
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install SSH key
+        uses: shimataro/ssh-key-action@v2
+        with:
+          key: ${{ secrets.SSH_KEY }}
+          known_hosts: ${{ secrets.KNOWN_HOSTS }}
+      - name: Use Node.js 12.x
+        uses: actions/setup-node@v1
+      - uses: actions/checkout@v2
+        with:
+          ref: demo
+      - run: npm install
+      - run: npm run build:prod
+      - run: rsync -r --delete-after dist/. "${{ secrets.REMOTE_URL }}":"${{ secrets.ADDRESS }}"