Support moving arrow relative to window, similar to H/M/L vim motions

[SpiritCroc]

Introduce a new PercentWindow step type, that allows you to move the cursor to relative position based on the items currently rendered on screen, similar as H/M/L ("high", "middle", "low") would do in vim.

Not added to default keybinding config since there are some conflicts, but you can put following to override:

{ on = "<S-H>", run = "arrow 0%-window", desc = "High: Move cursor to visible window top without scrolling" },
{ on = "<S-M>", run = "arrow 50%-window", desc = "Middle: Move cursor to visible window center" },
{ on = "<S-L>", run = "arrow 100%-window", desc = "Low: Move cursor to visible window bottom without scrolling" },

Which issue does this PR resolve?

#3969

Rationale of this PR

I got used to moving my cursor with "H"/"M"/"L" key bindings in applications supporting vim like motions. Since switching to yazi recently it has been constantly tripping me, that it is not possible to do.

AI disclaimer

I did use AI to write this for me. This means while I did read the code, question some AI decisions and iterated on them, and of course tested this myself, it's fair to point out I'm not an expert in this codebase.

[sxyazi]

This implementation looks wrong as it doesn't respect scrolloff, e.g. with scrolloff=5:

• H should jump to the 6th line within the window, not to the first line
• similarly, L should jump to the 6th-from-last line, not the last line.

Here's how Neovim behaves for H and L when you set :set scrolloff=5:

JtAlVouL.mp4

The same behavior can be reproduced in Vim too.

[SpiritCroc]

Ohhhh that makes sense, I never used scrolloff on (neo)vim, so it was off-putting for me and I worked around it for this change, sounds like I can simplify the patch then 👍

[SpiritCroc]

Hope I got the behaviour correct now.
BTW Thank you for the quick feedback, and for creating/maintaining yazi in the first place, greatly appreciated!