Add documentation for flag flipping

[ghostnaps]

First of all, thanks so much for the efforts put into this project to get it operational! After a lot of trial and error I managed to get Jest working with run-in-roblox, but this was quite challenging even for someone that actively deals with flags haha

My 2c: Documentation mentions flipping FFlagEnableLoadModule, but does not supply instructions for how. It would be great to include docs for how to do this on Windows and MacOS.

For Windows, explaining how to navigate to the appropriate version of Roblox Studio in Program Files, and creating the necessary ClientAppSettings.json file. It seems like there's some good info for this online already, so I don't expect Windows users to have as much of a problem, but still good to document

For MacOS, it took me a while to realize that ~/Library/Roblox/ClientSettings is not the correct place for this, and that I had to navigate to Applications/RobloxStudio.app/Contents/MacOS and manually create ClientSettings with ClientAppSettings.json inside it.

I now run a couple commands to do this for me:

mkdir -p /Applications/RobloxStudio.app/Contents/MacOS/ClientSettings
cp -R scripts/ClientAppSettings.json /Applications/RobloxStudio.app/Contents/MacOS/ClientSettings