fix(_root.scss): add custom properties - breakpoint-* and mobile-breakpoint

Author: xidedix

scss/_root.scss

@@ -8,6 +8,14 @@
     --#{$variable-prefix}#{$color}: #{$value};
   }
 
+  // breakpoints custom properties
+  @each $bp, $value in $grid-breakpoints {
+    --#{$variable-prefix}breakpoint-#{$bp}: #{$value};
+  }
+
+  // mobile breakpoint custom property
+  --#{$variable-prefix}mobile-breakpoint: #{$mobile-breakpoint};
+
   // Use `inspect` for lists so that quoted items keep the quotes.
   // See https://github.com/sass/sass/issues/2383#issuecomment-336349172
   --#{$variable-prefix}font-sans-serif: #{inspect($font-family-sans-serif)};