refactor: add critical CSS

Author: rstoenescu

src/components/icon/icon.mat.styl

@@ -1,6 +1,7 @@
 @import './core.variables'
 @import './variables.ios'
 @import './normalize'
+@import './critical'
 @import '../components/*/*.ios'
 @import './core/*'
 @import '../ie-compat/ie.ios'

src/components/icon/icon.ios.styl src/css/critical.stylsrc/components/icon/icon.ios.styl renamed to src/css/critical.styl

@@ -1,6 +1,7 @@
 @import './core.variables'
 @import './variables.mat'
 @import './normalize'
+@import './critical'
 @import '../components/*/*.mat'
 @import './core/*'
 @import '../ie-compat/ie.mat'