Core: Error Notifier

[5hirish]

Current Scope:

• [ ] Notify of errors in an non-intrusive way (specifically LSP errors)
• [x] Set notification levels
• [x] Expose notification provider
• [x] Auto dispose notification
• [ ] Notification slide-in and slide-out animation
• [ ] Flutter: Use as on overlay

Future Scope:

• Open Github Issue at g/quinine