Change editor selection behavior to more closely resemble windows behavior

[BartHageman]

Hi, I decided to have a go at changing the editor's selection behavior to more closely resemble windows explorer and other programs. It was discussed a while ago in the discord suggestions'. (I'm Mobius#4304) message here

New behavior (with l being the selected letter):

• no modifiers = Clear selection, add l to selection
• Ctrl = Add l to existing selection
• Shift = Add all letters from the last selected letter up to and including l to existing selection
• Ctrl + Shift = (See Shift)
• Alt = Clear selection and select word surrounding l (space delimited)
• Ctrl + Alt = Add word surrounding l to existing selection
• Shift + Alt = Same behavior as Shift, then afterwards select word (space delimited) around l
• Ctrl + Shift + Alt = (See Shift + Alt)

I did also change the fact that Ctrl blocks adding a letter to your selection if you're dragging an unselected letter around, for consistency's sake.

This is my first open source pull request ever, so let me know if I dun goofed somewhere. 😁

[DanRuta]

Thank you for the pull request, sorry it took this long 😅

The changes look good, and I briefly played around with it on v2 and it seemed to work fine - if anything comes up I'll add a fix for it.