Popup-keyboard for entering parens

[s-ol]

JuiceSSH has this nice feature of an (optional) overlay above the keyboard providing access to some keys that are not generally included or easy to access from normal OSKs. I think it would make sense to give access to ( ) [ ] { } # - in a similar fashion, as they are so commonly needed.

Here's a screenshot of JuiceSSH:

The extension-keyboard can be toggled by tapping anywhere on the screen above it, all other actions on the text are triggered using long-presses so there is no conflict.

[mfikes]

Related: replete-repl/replete-ios#62

[roman01la]

@s-ol I've put a small experiment in #20

I'm not sure yet about the toolbar, but it's certainly much easier to make than building a whole new keyboard 🤷‍♀️