fix(layout): conflict with [flex='initial']

*  fix CSS so `[flex] !== [flex="initial"]`
*  add `[flex="grow"]`

Author: ThomasBurleson

src/core/services/layout/layout.scss

@@ -192,7 +192,9 @@
   .#{$flexName},
   [#{$flexName}]               {  flex: 1 1 0%;  }
 
-  .#{$flexName},
+  .#{$flexName}-grow,
+  [#{$flexName}="grow"]        { flex: 1 1 100%;  }
+
   .#{$flexName}-initial,
   [#{$flexName}="initial"]     {  flex: 0 1 auto;  }