Adding Heroku deploy action (#485)

Author: chriswedgwood

.github/workflows/heroku-deploy.yml

@@ -0,0 +1,24 @@
+name: Push Container to Heroku
+
+on: 
+  push:
+    branches:
+      - main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Login to Heroku Container registry
+      env: 
+        HEROKU_API_KEY: ${{ secrets.HEROKU_API_KEY }}
+      run: heroku container:login 
+    - name: Build and push
+      env:
+        HEROKU_API_KEY: ${{ secrets.HEROKU_API_KEY }}
+      run: heroku container:push -a djangosnippets web 
+    - name: Release
+      env:
+        HEROKU_API_KEY: ${{ secrets.HEROKU_API_KEY }}
+      run: heroku container:release -a djangosnippets web