feat(kanata): add ultrawide mod

[Iorvethe]

This mod is in essence the wide mod applied to both hands, shifting them by one column each. This is super useful when using Arsenik on a regular staggered keyboard as the [LAlt] is quite uncomfortable to reach (as is the [RAlt] without the wide mod) and may in the long term cause RSI on the thumbs, which would be quite ironic for an ergonomic layout!

The advantages I see are:

• More comfortable [LAlt] which is extensively used
• Hands further apart, even closer to a split keyboard
• Potentially usable on keyboards with space-bars of >5 units

The possible drawbacks could be:

• Loss of all keys on the left side such as [Tab], [LShift], etc.
  • Should these be used with Arsenik anyway?
• Loss of home bumps, so harder to reposition without looking at the keyboard
  • Easily solvable by either swapping the physical keys or by taping a DIY bump on the keys (what I did)
• In case of a narrow physical keyboard, the left hand would rest on an edge which could be uncomfortable

The drawbacks are few and the increased comfort is such that I think the mod has its place in the project. I have been daily-driving this mod for a few weeks and it is so much better, very usable and a joy to type with such a small part of my keyboard!

A few TODOs before merging (if accepted):

• Not sure about the name (or whether there is an agreed-upon name in the wider community for something similar)
• Add a note about the wide mods in the README and caution about the potential RSI by not using them