Cache docker build

Author: tannewt

.github/workflows/build-zephyr-container.yml

@@ -52,6 +52,9 @@ jobs:
             type=sha
             type=raw,value=latest,enable={{is_default_branch}}
 
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
       - name: Build and push
         uses: docker/build-push-action@v6
         with:
@@ -60,6 +63,8 @@ jobs:
           push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
 
       - name: Set image reference output
         id: image-ref