Use the new builtin `nvim_set_keymap()` `desc` option for WhichKey integration

[b0o]

This would dramatically simplify the code by obviating the need for direct coupling with WhichKey.

This can be partially implemented immediately by passing the desc option to nvim_set_keymap(), but the removal of WhichKey-specific code depends on folke/which-key.nvim#253 / folke/which-key.nvim#242.

[towry]

Both upstream dependencies seem resolved, tag blocked can be removed ?

[b0o]

Yes, thanks for reminding me @towry – I don’t have time to work on this right now but I’m open to PRs.