Permission denied on k6 docker json output

@mstoykov Thanks!

$ docker run -i -v $(pwd):/ci/ --user $UID loadimpact/k6:latest run --out json=/ci/result.json /ci/performance-test.js
it works!

and I can use it on circleci!
https://app.circleci.com/pipelines/github/sanemat/faas-penguin/57/workflows/6d76e983-49f5-49ec-81a6-16e753775aa6/jobs/78/artifacts
This is circleci example: