GH Action to publish updated image

.github/workflows/docker-image.yml

@@ -0,0 +1,45 @@
+name: Docker Image CI
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+env:
+  THIS: "ebullient/pandoc-emoji"
+  TAG: "3.1"
+
+jobs:
+
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Extract metadata (tags, labels) for Docker
+      id: meta
+      uses: docker/metadata-action@v4
+      with:
+        images: ${{ github.repository }}
+        tags: |
+          type=schedule,pattern={{date 'YYYYMMDD'}}
+          type=raw,value=latest,enable={{is_default_branch}}
+          type=raw,enable=true,priority=200,prefix=,suffix=,value=${{ env.TAG }}
+
+    - name: Login to Docker Hub
+      if: github.ref == 'refs/heads/main'
+      uses: docker/login-action@v2
+      with:
+        username: ${{ secrets.DOCKERHUB_USERNAME }}
+        password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+    - name: Build and push Docker image
+      if: github.repository == ${{ env.THIS }} && github.ref == 'refs/heads/main'
+      uses: docker/build-push-action@v3
+      with:
+        context: .
+        push: true
+        tags: ${{ steps.meta.outputs.tags }}
+        labels: ${{ steps.meta.outputs.labels }}