Add action to push alpine images to Docker Hub

Add a GitHub action to push alpine images with curl-impersonate to
Docker Hub whenever a new release tag is created.

.github/workflows/publish-docker-image.yml

@@ -0,0 +1,42 @@
+# Build an Alpine Linux image containing curl-impersonate and push to
+# Docker hub.
+name: Publish Docker image
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+jobs:
+  push-docker-image:
+    name: Push Docker image to Docker Hub
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out the repo
+        uses: actions/checkout@v2
+
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta_chrome
+        uses: docker/metadata-action@v3
+        with:
+          images: lwthiker/curl-impersonate
+          tags: |
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+          flavor: |
+            suffix=-chrome-alpine3.15
+
+      - name: Build and push the Chrome version of curl-impersonate
+        uses: docker/build-push-action@v2
+        with:
+          push: true
+          context: chrome/
+          file: chrome/Dockerfile.alpine
+          tags: ${{ steps.meta_chrome.outputs.tags }}
+          labels: ${{ steps.meta_chrome.outputs.labels }}