Use official buildx action (#6)

Author: jvanbruegge

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
         uses: actions/checkout@v2
 
       - name: Setup buildx
-        uses: crazy-max/ghaction-docker-buildx@v3
+        uses: docker/setup-buildx-action@v1
 
       - name: Cache docker layers
         uses: actions/cache@v1