EntityTeleportEvent Not Called When ActiveMob Gets Leashed

Summary

When a mob is teleported via its spawner's leash, the EntityTeleportEvent is not called.

Steps to reproduce

1. Create a MythicMob Spawner
2. Have the Spawner leash its mobs
3. Aggro a mob, and get it to walk far enough that it teleports back due to the leash.
4. Have a listener listening to the EntityTeleportEvent - notice that it does not get called.

Current behavior

The EntityTeleportEvent is not called.

Intended correct behavior

The EntityTeleportEvent, or a similar custom event (e.g. MythicMobTeleportEvent or ActiveMobTeleportEvent or AbstractEntityTeleportEvent) should be called.

Proposed fixes

Create an event for when a MythicMob gets leashed.