Add GitHub action to publish container (#7)

* First pass at github action

* Update repo name for testing

* revert to official repo name

Author: rothgar

.github/workflows/main.yml

@@ -0,0 +1,31 @@
+name: main
+
+on:
+  push:
+    branches: main
+
+jobs:
+  login:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check Out Repo
+        uses: actions/checkout@v2
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Login to Public ECR
+        uses: docker/login-action@v1
+        with:
+          registry: public.ecr.aws
+          username: ${{ secrets.AWS_ACCESS_KEY_ID }}
+          password: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
+        env:
+          AWS_REGION: us-east-1
+
+      - name: Build and push container
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          push: true
+          tags: public.ecr.aws/aws-containers/hello-app-runner:latest