renamed `.text-xs` to `.text-md` and created a correct `.text-xs`

build/scss/_text.scss

@@ -9,11 +9,15 @@
   }
 }
 
+.text-xs {
+  font-size: $font-size-xs !important;
+}
+
 .text-sm {
   font-size: $font-size-sm !important;
 }
 
-.text-xs {
+.text-md {
   font-size: $font-size-base !important;
 }