Add option to draw layout associated to register on the same plot as the Register

[a-corni]

It is currently hard to visualize what trapping spots have been selected among a layout to define a Register. The layout is stored inside a register. With the option "qubits_color", we can implement the plotting of both layout and register on the same plot:

Suggested by both @SergiJulia94 and @soufianekaghad98

[BrFle]

Hey ! I'd like to start contributing to Pulser, can I be assigned this issue ?

[HGSilveri]

Hey @BrFle , of course! Let us know if you need any help :)