Add button/short-cut to activate a specific line of code

[Marsel Ishimbaev]

Now all the code is activated sequentially in order.
But sometimes it is of use to sound only one specific line of code at a time.
It gives freedom to decide what to play not using pesky commenting / uncommenting.
It can be implemented as a separate button activating the line on the cursor or a short-cut (like in Supercollider).

[Damien Clarke]

Yeah I'm very keen for this - covered by this task #1. I'll close as this is a duplicate, thanks for logging this!