Please add multi-selection support

[fsateler]

It is currently missing (and known missing), so I thought having a place where interested parties could to discuss advances/possibilities could help.

Unfortunately, I do not know how to implement this. However, if anyone has ideas as to how this could be done, please share them.

[Cellule]

I became dependent on that feature using CTRL + D in sublime. Now I feel like I'm missing something when I go back to Visual Studio. I unfortunately don't know how to make an extension for Visual Studio, but I would be more than interested to tackle this.