fix（handles）: fix the README checking issue

Author: stephen-zeng

server/handles/down.go

@@ -131,7 +131,7 @@ func localProxy(c *gin.Context, link *model.Link, file model.Obj, proxyRange boo
 	Writer := &common.WrittenResponseWriter{ResponseWriter: c.Writer}
 
 	//优先处理md文件
-	if utils.Ext(file.GetName()) == "md" && setting.GetBool(conf.FilterReadMeScripts) {
+	if file.GetName() == "README.md" && setting.GetBool(conf.FilterReadMeScripts) {
 		buf := bytes.NewBuffer(make([]byte, 0, file.GetSize()))
 		w := &common.InterceptResponseWriter{ResponseWriter: Writer, Writer: buf}
 		err = common.Proxy(w, c.Request, link, file)