dtc2d: editor opens to 3D view due to main class node type

[insomniacUNDERSCORElemon]

Godot does not seem to associate Node with 2D. I've tested this and it seems to be fixed by changing the node type to Control.

Additionally, import Node doesn't seem to be needed (or for Control, either) I assume because no related functions are actually being used (maybe there's nuance I am missing, but it compiles and no features seem to break).

Beyond that change, there are 2 other needed changes:

• set main node to full rect (so the ColorRect properly works)
• remove reference to this issue in readme

If I am not missing some importance, I can make these changes.