[Feature]: Update appointment timeslot on tile drag

[(ツ)_/¯Kiafuka]

When a user drags a appointment tile, we should:

• Update start and end time based on where the tile is currently.
• Timeslots should be of 15min diff

Code Pointers
https://github.com/brunokiafuka/drag-cal/blob/da0f9307600b2a24d5d4c2b55158102dde165b06/src/Appointment.tsx#L16