use github actions caching for docker build

Author: haarg

.github/workflows/build-container.yml

@@ -32,6 +32,8 @@ jobs:
         with:
           target: test
           push: false
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
       - name: Run Perl tests
         run: docker run -i ${{ steps.docker-build-test.outputs.imageid }}
       - name: Docker meta
@@ -52,6 +54,8 @@ jobs:
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           annotations: ${{ steps.meta.outputs.annotations }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
       - name: Update deployed image
         if: ${{ contains( fromJSON(steps.meta.outputs.json).tags, format('{0}:latest', github.repository)) }}
         uses: benc-uk/workflow-dispatch@v1