Today I can call vscode.openFolder to open a folder programmatically:

vscode.commands.executeCommand("vscode.openFolder", vscode.Uri.file(path), false);

However, I would like to be able to do the same thing with the new multi-root workspace and just add a folder to the workspace. Something like this, but where I can pass in a Uri

For more context on our scenario, see @chrisdias's comments on this issue: #13807

NOTE: We realize such a command might restart the extension host, but we don't care if that happens.