Add github image CI

.github/workflows/build-and-push-image.yml

@@ -0,0 +1,44 @@
+name: Build and push image
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  build_and_push_image:
+    name: Build Docker image and push to registries
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Login to DockerHub
+        uses: docker/login-action@v1 
+        with:
+          username: charlocharlie
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v1 
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build and push
+        id: docker_build_push
+        uses: docker/build-push-action@v2
+        with:
+          push: true
+          tags: |
+            charlocharlie/markov-discord:latest
+            ghcr.io/${{ github.repository }}:latest
+            ghcr.io/${{ github.repository }}:${{ github.sha }}
+
+      - name: Image digest
+        run: echo ${{ steps.docker_build_push.outputs.digest }}