Spaceline support

[taingra]

Spaceline is the powerline theme for spacemacs, but it's more than just a theme for powerline. Its a complete powerline implementation with way more features than emacs powerline. It can also be used in Emacs without Spacemacs dependencies. Please consider adding support for this

[kuanyui]

Sorry, recently I have no time to install, read manuals then adjust the color balance for each new, cutting-edge packages, especially those which I've never used nor will use. Please consider push a PR with a screenshot and I will merge it. Thanks. 🙇‍♀️ 🙇‍♂️