add more files

src/utils/index.js

@@ -1,8 +1,11 @@
 import ArtPlayerError from './ArtPlayerError';
-export * from './verification';
 
 export function errorHandle(condition, msg) {
   if (!condition) {
     throw new ArtPlayerError(msg);
   }
 }
+
+export function clamp(num, a, b) {
+  return Math.max(Math.min(num, Math.max(a, b)), Math.min(a, b));
+}