Add Arc-Black color variant as an option #134
Description
Hi,
I wanted to suggest adding Arc Black color scheme in this package as I found that it makes a pleasant difference in contrast to arc dark variation. Arc Black has been my default style for GTK, but unfortunately it is still not available through Kvantum.
According to author: "The black Arc desktop theme darkens only six elements, on the whole, but where it happens makes all the difference. Significantly, keeping the official Arc hues, contrasts, and structure wholly intact was foremost in this project's objective. Thus, nothing is altered one tiny bit in those crucial areas - as the existent, intact, Arc hues are pragmatically darkened."
This means that minimal changes were made, but the difference is not small, as can be seen in the screenshots below.
