add select to copy option

[RichardKraus]

first of all: thank you for the awesome terminal, I am loving it so far.

One thing I keep stumbling upon however, is the lacking support for select to copy (at least I couldnt find any option to turn it on). I use this feature a lot in other terminals and additional button presses are always a bit annoying. If I already move my mouse to mark something, I usually always want it to end up in my clipboard.

[RichardKraus]

I realized that this is just a mirror. Ill raise an issue upstream.