feature: display quantity of items within the hotbar

[Gorgaki]

I'm thinking of a very simple feature that could improve the player experience.
Display the quantities of items owned in the hotbar.

[EspectroW94]

I was just thinking about proposing this idea, I think it would be very useful.

[Arufonsu]

Added to (v0.8.0-beta.120+) Roadmap

[Arufonsu]

solved by #2342