Use actions to login to GHCR (issue space-ros#193)

.github/workflows/earthly-build.yaml

@@ -34,6 +34,12 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v3
+      - name: Login to ghcr
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
       - name: Set up earthly
         run: |
           sudo wget https://github.com/earthly/earthly/releases/latest/download/earthly-linux-amd64 -O /usr/local/bin/earthly
@@ -54,5 +60,4 @@ jobs:
       - name: Push the main spaceros image to GHCR
         if: ${{ github.ref_name == '212/merge' }}
         run: |
-          echo "${{ secrets.GITHUB_TOKEN }}" | docker login ghcr.io -u ${{ github.actor }} --password-stdin
           earthly --ci --push +push-image --TAG="ghcr.io/space-ros/space-ros:push-main-image" --LATEST=""