modify initial parameter for artist list

router/artist_list.js

@@ -22,14 +22,14 @@ module.exports = (req, res, createWebAPIRequest, request) => {
   // 其他女歌手 4002
   // 其他组合/乐队 4003
 
-  // initial 取值A为65,B为66...以此类推
+  // initial 取值a-z/A-Z
 
   const data = {
     categoryCode: req.query.cat || "1001",
     offset: req.query.offset || 0,
     total: req.query.total ? "true" : "false",
     limit: req.query.limit || 30,
-    initial: req.query.initial || ""
+    initial: (req.query.initial || "").toUpperCase().charCodeAt() || ""
   };
   createWebAPIRequest(
     "music.163.com",