feat(build-push-to-dockerhub): enable docker mirror for buildx on self-hosted runners (#999)

* feat(build-push-to-dockerhub): enable docker mirror for buildx on
self-hosted runners

* revert testing changes

Author: ricky-undeadcoders

actions/build-push-to-dockerhub/action.yaml

@@ -94,6 +94,7 @@ runs:
       uses: docker/setup-buildx-action@b5ca514318bd6ebac0fb2aedd5d36ec1b5c232a2 # v3.10.0
       with:
         driver: ${{ inputs.docker-buildx-driver }}
+        buildkitd-config: ${{ runner.environment == 'self-hosted' && '/etc/buildkitd.toml' || '' }}
 
     - name: Extract metadata (tags, labels) for Docker
       id: meta