use docker scopes to try and improve caching

.github/workflows/staging-ghcr-public.yml

@@ -1,4 +1,3 @@
-
 name: Publish to ghcr (staging)
 
 on:
@@ -63,8 +62,10 @@ jobs:
         with:
           context: .
           labels: ${{ steps.meta.outputs.labels }}
-          cache-from: type=gha
-          cache-to: type=gha,mode=max
+          cache-from: |
+            type=gha,scope=${{ matrix.platform }}
+          cache-to: |
+            type=gha,mode=max,scope=${{ matrix.platform }}
           platforms: ${{ matrix.platform }}
           outputs: type=image,name=${{ env.REGISTRY_IMAGE }},push-by-digest=true,name-canonical=true,push=true
           build-args: |