introduce GitHub Action to build container (#4)

introduce gh action

.github/workflows/build.yml

@@ -0,0 +1,29 @@
+name: Build and Publish Docker
+
+on:
+  push:
+    branches: [ main ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v2
+
+    - name: Set up Docker Buildx
+      uses: docker/setup-buildx-action@v1
+
+    - name: Login to DockerHub
+      uses: docker/login-action@v1 
+      with:
+        username: ${{ secrets.DOCKERHUB_USERNAME }}
+        password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+    - name: Build and push
+      uses: docker/build-push-action@v2
+      with:
+        context: .
+        push: true
+        tags: tillepille/diagrams:latest