chore: update Docker image publish workflow

* Use official action to log in to Docker Hub
* Run using pinned ubuntu-20.04 environment

Author: jawnsy

.github/workflows/docker.yaml

@@ -6,23 +6,33 @@ on:
   workflow_dispatch:
 
   release:
-    types: [released]
+    types:
+      - released
+
+  pull_request:
+    branches:
+      - main
 
 jobs:
   docker-images:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2
+      - name: Checkout
+        uses: actions/checkout@v2
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v1
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v1
 
+      - name: Login to Docker Hub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+
       - name: Run ./ci/steps/docker-buildx-push.sh
         run: ./ci/steps/docker-buildx-push.sh
         env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-          DOCKER_USERNAME: ${{ secrets.DOCKER_USERNAME }}
-          DOCKER_PASSWORD: ${{ secrets.DOCKER_PASSWORD }}
+          GITHUB_TOKEN: ${{ github.token }}

ci/steps/docker-buildx-push.sh

@@ -26,11 +26,6 @@ main() {
   # Download the release-packages artifact
   download_artifact release-packages ./release-packages
 
-  # Login to Docker
-  if [[ ${CI-} ]]; then
-    echo "$DOCKER_PASSWORD" | docker login -u "$DOCKER_USERNAME" --password-stdin
-  fi
-
   docker buildx bake -f ci/release-image/docker-bake.hcl --push
 }