Implement alert, confirm and prompt message boxes

[DivineOmega]

Implement multi-platform message boxes:

• Alert
• Confirm
• Prompt

[DivineOmega]

Consider using this promise-based message box replacement library -> https://github.com/coderaiser/smalltalk

[DivineOmega]

Actually, this library may not be sufficiently multi-platform. It may be best to implement these message boxes on canvas (perhaps as a persistent scene).