🎯 `Layer` Definition

[eoussama]

This issue details the Layer object and explains its role and purpose.

A layer is auto-created whenever a new textdraw is added to the board. A textdraw element may or may not be associated with a layer, having said that, a present textdraw on the board should always be associated with a layer that controls its visibility, write mode (read-only), and render order.

Layers provide the following features:

• Visibility control
• Write/Read mode
• Affects textdraw render order
• Terminates associated textdraw when deleted

[eoussama]

Layers have been dumped in favor for normal textdraws, each textdraw is treated as a layer anyway.