ci (docker.yml): use registry image cache

Author: pythoninthegrass

.github/workflows/docker.yml

@@ -100,5 +100,9 @@ jobs:
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
           platforms: linux/amd64,linux/arm64/v8
-          cache-from: type=gha
-          cache-to: type=gha,mode=max
+          cache-from: |
+            type=gha,scope=${{ github.workflow }}
+            type=registry,ref=ghcr.io/${{ env.REGISTRY_USER }}/${{ env.IMAGE }}:buildcache
+          cache-to: |
+            type=gha,scope=${{ github.workflow }},mode=max
+            type=registry,ref=ghcr.io/${{ env.REGISTRY_USER }}/${{ env.IMAGE }}:buildcache,mode=max