add Docker Desktop WSL issue warning to getting started docs

When using WSL and Docker Desktop, the user needs to complete the installation by following [the linux post-installation steps](https://docs.docker.com/engine/install/linux-postinstall/#manage-docker-as-a-non-root-user) to avoid the error `docker: Error response from daemon: Ports are not available`.

See @martinovicdev 's comment on issue #347 for more info.

