"Launch Multiplayer" button isn't descriptive enough

[ASpoonPlaysGames]

Fairly often we get people coming into discord asking for help because the "Launch Multiplayer" button is locked, and they don't notice the "Launch Northstar" button.

It should be changed to read something like "Launch Vanilla" to help stop people from autopiloting it a bit, and also to be more descriptive with the form of multiplayer that it would launch.

This would also help for if/when vanilla compatibility is reintroduced.