Add setting to keep focus in the same place

[willwade]

Add a setting to only ever show the current level of the tree, this will mean the currently focused item will never shift around the screen, this helps people with certain conditions.

Original Issue

For some individuals with PSP who have difficulty shifting their gaze a v minimal visual display is required. Ie no view of before or after tree - just the current highlighted word/letter/phrase

Something like
https://shwr.me/#10 or
https://impress.js.org/#/bored

NB: #119 would also need to work with this 'mode'

[gavinhenderson]

Hey @willwade Can i just clarify my understanding of this issue?

So for up and down the highlighted word never actually moves (by design I imagine)

And you want an option to make that the case for left and right aswell?

So in theory we just want to only show the current level of tree? Meaning that the highlighted word never ever moves even as you go down a tree.

Sound like a good idea! Just wanted to make sure I was on the same page

[willwade]

Thats it!