Keybind for Extend/shrink selection up and down

[EmiOnGit]

Currently helix seem to lack a lack a intuitive way to extend/shrink the selection down or up based on direction of selection.

With extend/shrink a line down I'm basically speaking about the default x-key with the change that it shrinks the selection if the direction is reversed.

Besides that I also would love to have a counterpart to the 'changed' x-key described above.
This would extend/shrink the line above dependent on the direction of selection.

I would suggest to implement the commands without binding them by default, especially to give people the opportunity to test them out properly.
Personally, I would love these two commands to be bound to the J,K keys since it works very intuitively.

I've seen a wish for this behavior a couple of times already in the help-forums as well as in the keymap discussion e.g.:
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[david-crespo]

This is closed by #9080, right? It didn't auto-close because the message didn't say "closes" or "fixes".