Better `ekzo-bg`

[ArmorDarks]

Replace

// ---------------------------------------
// Background
// ---------------------------------------

$ekzo-bg: $ekzo-bg-color;

with maps, or separate variables.

They should handle such parameters:

$ekzo-bg: url('#{$ekzo-images-path}/bg--hero.jpg') fixed center 290px $ekzo-bg-color;

[ArmorDarks]

Declined, since it will make this property value unflexible