CI: add deploy step to GitHub Actions

.github/workflows/nodejs.yml

@@ -13,7 +13,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [13.x]
+        node-version: [14.x]
 
     steps:
     - uses: actions/checkout@v2
@@ -23,3 +23,21 @@ jobs:
         node-version: ${{ matrix.node-version }}
     - run: yarn
     - run: yarn build
+
+  deploy:
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: docker/setup-buildx-action@v1
+      name: Setup Docker BuildX system
+    - name: Login to DockerHub
+      uses: docker/login-action@v1 
+      with:
+        username: ${{ secrets.DOCKERHUB_USERNAME }}
+        password: ${{ secrets.DOCKERHUB_TOKEN }}
+    - uses: docker/build-push-action@v2
+      name: Deploy the image
+      with:
+        push: true
+        tags: citraemu/discord-bot:latest