Feature Request: Corner radii

[leb-kuchen]

The appearance settings has 3 options for corner radii. These are the generated config files in CosmicTheme{Dark,Light} respectively. There is a builder, but for corner radii these values are the same. Also these values are for top-left, top-right, bottom-right and bottom-left

(
    radius_0: (0.0, 0.0, 0.0, 0.0),
    radius_xs: (4.0, 4.0, 4.0, 4.0),
    radius_s: (8.0, 8.0, 8.0, 8.0),
    radius_m: (16.0, 16.0, 16.0, 16.0),
    radius_l: (32.0, 32.0, 32.0, 32.0),
    radius_xl: (160.0, 160.0, 160.0, 160.0),
)
(
    radius_0: (0.0, 0.0, 0.0, 0.0),
    radius_xs: (2.0, 2.0, 2.0, 2.0),
    radius_s: (8.0, 8.0, 8.0, 8.0),
    radius_m: (8.0, 8.0, 8.0, 8.0),
    radius_l: (8.0, 8.0, 8.0, 8.0),
    radius_xl: (8.0, 8.0, 8.0, 8.0),
)
(
    radius_0: (0.0, 0.0, 0.0, 0.0),
    radius_xs: (2.0, 2.0, 2.0, 2.0),
    radius_s: (2.0, 2.0, 2.0, 2.0),
    radius_m: (2.0, 2.0, 2.0, 2.0),
    radius_l: (2.0, 2.0, 2.0, 2.0),
    radius_xl: (2.0, 2.0, 2.0, 2.0),
)

So what options should we provide? I think of 2 options.

1. Let the user set config file
2. Provide more options than the appearance settings with a slider