[Feature Request] show icons in signcolumn

[igorlfs]

Hello!

Thanks for the really nice plugin! I do have suggestions / feature requests regarding the icons.

The first suggestion is to have an option to show the icons in the signcolumn, similarly to how there's an inlay option. In addition, it would be nice to have highlight groups defined for the icons. Currently, the default config uses emojis, which "hide" the need for proper highlighting. There could be (at least) four highlights groups: one for each state of the icons and another for the time the request took.