Add script to automatically side-load distros for WSL

Aside from the user downloading the required tar.gz file and renaming to install.tar.gz (which could also be part of the automation process), there should be a way to automate the https://github.com/Microsoft/WSL-distrolauncher process so we can side-load distros not currently in the Store without going through the build process itself (a time-consuming effort). I would recommend pulling the Docker images if we do automate the download of distros. All of this would be commented out by default. Best place currently to place this is in the dev_app.ps1 script.