Add key commands for inventory hotswap.

[ghost]

1. Add the ability to use ctrl+[1-4] to quickly switch to a different hotbar loadout. I imagine it to work like harpoon.vim, or i3-wm's workspaces. Instead of swapping an inventory row with the hotbar, Ctrl+n will always give you the nth row.

2. Change the inventory UI to match. Instead of 3 inventory rows + hot bar, simply have 4 inventory rows.

3. Because ctrl+[1-4] might overlap with existing commands on the user's machine, add an option to change the key maps.

4. In the future, potentially add a key map to hot swap full shulkerboxes into the inventory, or specific rows in the shulkerboxes.

I am willing to work on this, though I am not experienced with modding minecraft, or Kotlin, so I have no idea how hard this will be to do. Any help would be appreciated to set it up, and critiques are welcome.

[kikugie]

I vote more for making https://www.modrinth.com/mod/hotbarcycle an optional dependency.
I usually judge it by how easy it is to implement a feature versus the quality of existing implementations. HotbarCycle does it well and it would be a waste of time to reimplement all of it.