Feature request - option to prevent selecting the justl buffer when running

[bbbscarter]

At the moment when you run a justl command, input focus shifts to the justl buffer. Depending on what you're doing this isn't always what you want - e.g. in the case of using justl to issue compilation commands, you might want it to behave like a standard compilation buffer.

Having an option to toggle this behaviour would be useful.

PR incoming!

[psibi]

Fixed by #68