Create NOTIFICATION_DELETE in IPC

[RecklessBoon]

It would be nice to have the compliment of the NOTIFICATION_CREATE IPC event so as to be able to cache and clear notifications properly. Currently there is no way to tell if someone has read through a previously cached notification on their client. Channel ID and Message object would be a reasonable dispatch payload for this.

[erkinalp]

Unfortunately, the current read state structure in Discord is not suitable for that: Read receipts in Discord function more like fully read markers, as they are rewindable and tightly coupled to notifications.