[Feature] Ability to change the cursor in the header on WIndows FullScreen

I have been trying to get vim-like keybindings to work with a Normal/Insert mode, and while I was successful I have failed to find a way to change the cursor when in full screen mode.
From what I gather on Windows it is using tcell to render, and the caret/cursor is hardcoded to a block.
TCell has the ability to change the cursor, so it would be great if that could be exposed like `--bind=start:change-cursor-style(steady-bar)`.

Trace fzf's Windows full-screen rendering and the tcell cursor handling described in the issue, then inspect how --bind actions are parsed and applied. The work is done when a binding such as start:change-cursor-style(steady-bar) changes the cursor style in full-screen mode on Windows, with coverage for the supported behavior.

Written by the indexing model from the issue text.