Draft: Add Tav new spin button to lpe sketch

This is a test of a new concept for spin buttons made by TAV. https://gitlab.com/Tavmjong/gtk_sandbox/-/tree/master/gtkmm_spinbutton

It was added just to LPE Sketch to test how it feels to use. In the future it would replace all spin buttons.

delivery to : ux#25

How to test: create object add LPE sketch to it in LPE panel

TODO:

• Ask gimp devs for his code to infinite scroll nedded to implement well this.
• change the style and formating
• [ ]

Demo: