Update GitHub Actions workflow to use GitHub Container Registry for D…

…ocker image login and tagging

.github/workflows/docker-image.yml

@@ -19,15 +19,16 @@ jobs:
     - name: Set up Docker Buildx
       uses: docker/setup-buildx-action@v1
 
-    - name: Login to DockerHub
+    - name: Login to GitHub Container Registry
       uses: docker/login-action@v1
       with:
-        username: ${{ secrets.DOCKER_USERNAME }}
-        password: ${{ secrets.DOCKER_PASSWORD }}
+        registry: ghcr.io
+        username: ${{ github.repository_owner }}
+        password: ${{ secrets.GITHUB_TOKEN }}
 
     - name: Build and push Docker image
       uses: docker/build-push-action@v2
       with:
         context: .
         push: true
-        tags: ${{ secrets.DOCKER_USERNAME }}/posh-rest:latest
+        tags: ghcr.io/${{ github.repository_owner }}/posh-rest:latest