Fix icons purged by purgecss

gulpfile.js

@@ -43,7 +43,7 @@ const postcssPurgecss = require("@fullhuman/postcss-purgecss")({
     /row-span-\d\d?/, // grid spans
     /(sm|md|lg|xl)(\\:)text-.*/,
     // /text-*/,
-    /^ico--[a-z]+\:before$/, // icons
+    /ico--*/, // icons
   ],
 });