FIx#862
In Unity 2020.1 TMpro is auto updated to 3.0.x and there is a slight behaviour change from TMPro 2.x that requires us to be more thorough is our use of maxVisibleCharacters.
Add TheExperiement_TMPro
Added DragAndDrop example scene
Added Clickable2D and Draggable2D components to make sprites clickable
and draggable.
Added event handlers which list for events from the Clickable2D and
Draggable2D components.