style: Replace .btn_radius by .circular and .image-button

[Kekun]

Let's use the standard style classes here. This also fixes the outline's
radius.

[mirkobrombin]

I've been looking for class documentation for a long time, do you have a References link?

[Kekun]

Sadly there isn't a documentation of the Adwaita stylesheet AFAIK, but some widgets document classes affecting them in their documentation in a "CSS node" section, e.g. .circular is documented here: https://developer.gnome.org/gtk3/stable/GtkButton.html

That's probably something we should improve with libadwaita.

[mirkobrombin]

Sadly there isn't a documentation of the Adwaita stylesheet AFAIK, but some widgets document classes affecting them in their documentation in a "CSS node" section, e.g. .circular is documented here: https://developer.gnome.org/gtk3/stable/GtkButton.html

That's probably something we should improve with libadwaita.

Yes, this would definitely be a huge improvement. Thanks so much!