creating tests/running container with env vars

as [reported by Jonathan here](https://www.patreon.com/posts/introduction-to-46154446)

> Running tests on lokl/lokl did not work for me until I set LOKL_RELEASE_VERSION var before other vars on lokl-cli:

```
LOKL_RELEASE_VERSION="5.0.0-dev"
LOKL_DOCKER_TAG="$(set_docker_tag)"
LOKL_NAME="$(set_site_name)"
LOKL_PORT="$(set_site_port)"
```

> I also noticed after using the new docker image I am no longer able to upload a custom theme (get ftp screen). I assume this is due to a permission issue on the file system but only just started playing with the Dockerfile.