Customize screenshot directory path

[TwitchBronBron]

It would be nice to allow developers to override the default screenshot directory, as right now it uses the OS's temp dir.

• Define a new user setting called brightscript.screenshotDir here in the miscellaneous group.
• You can retrieve the setting with this code:

  vscode.workspace.getConfiguration('brightscript').get<string>('screenshotDir');
  

• We capture the screenshot here. I think you need to set outDir as a property in that object that is passed to rokuDeploy.takeScreenshot()