Fix publishing Docker image to GitHub

.github/workflows/CI.yml

@@ -3,7 +3,7 @@ on: pull_request
 
 jobs:
   test:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
 
     steps:
       # Check out, and set up the node/ruby infra

.github/workflows/publish_package.yml

@@ -0,0 +1,28 @@
+name: Release Danger-JS package
+
+on:
+  push:
+    tags:
+      - '*'
+
+jobs:
+  build:
+    runs-on: ubuntu-20.04
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Export tag version
+        run: echo "VERSION=${GITHUB_REF/refs\/tags\//}" >> $GITHUB_ENV
+
+      - name: Docker Login
+        run: echo $PACKAGES_WRITE_TOKEN | docker login ghcr.io -u $USERNAME --password-stdin
+        env:
+          PACKAGES_WRITE_TOKEN: ${{ secrets.DOCKER_GITHUB_PASSWORD }}
+          USERNAME: ${{ secrets.DOCKER_GITHUB_USERNAME }}
+
+      - name: Docker Build
+        run: docker build -t ghcr.io/danger/danger-js:$VERSION .
+
+      - name: Deploy
+        run: docker push ghcr.io/danger/danger-js:$VERSION