Change Docker login to use GHCR credentials

Updated Docker login credentials for GitHub Container Registry.

.github/workflows/docker-image.yml

@@ -58,8 +58,8 @@ jobs:
         uses: docker/login-action@v3
         with:
           registry: ghcr.io
-          username: ${{ github.actor }}
+          username: lukegus
-          password: ${{ secrets.GITHUB_TOKEN }}
+          password: ${{ secrets.GHCR_TOKEN }}
 
       - name: Login to Docker Hub
         if: github.event.inputs.registry == 'dockerhub'