docs(developer): tutorial for BECWidget base class
Description
Added section about BECWidget base class and how BECConnector works like. In next MR I will ended it by step-by-step tutorial how to create widget with this approach and that why it is important to at least write a basic test for your new widget.
Related Issues
relates #284 (closed), #289 (closed)
Type of Change
- docs new section