Support for multiroot workspaces with game setting

[rjstone]

Is your feature request related to a problem? Please describe.
Multiroot workspaces aren't currently supported. Any code that retrieves workspace root folders just uses the first folder. Also there is no setting for which game is associated with the folder.

Describe the solution you'd like
Support multiroot workspaces and place a hidden setting in the root folder .vscode/settings.json to indicate the game that is associated with the folder. This can be done automatically by project file generation so the user doesn't need to be bothered with it.

Describe alternatives you've considered
Just doing nothing and continuing to guess at what game a folder is for based on heuristics, or use the game in the PPJ.

Additional context
While it's not needed for PPJ builds, things like "compile current file" and "compile on save" would need information on which game should be used.

[joelday]

@nikitalita Multiroot workspace support is needed in general. Can ignore the suggestions above (especially since we want to get out of the business of owning opinionated project templates, etc.)