support completion of values enclosed in quotes

[rsteube]

e.g.

example "ac<TAB>
# example "action"

• [x] bash
• [x] elvish
• [ ] fish
• [ ] ion
• [ ] nushell
• [ ] oil
• [ ] powershell
• [ ] xonsh
• [ ] zsh

related #6

[rsteube]

• test if quotes are matched using echo echo '"'example | xargs echo
• if fails update values to be inserted to fix escaped space echo 'a\ b\ c | xargs echo