feat(player): 倍速改为底部弹窗选择

lib/l10n/app_localizations_zh.dart

@@ -136,6 +136,9 @@ class AppLocalizationsZh extends AppLocalizations {
   @override
   String get exitClearScreen => '退出清屏';
 
+  @override
+  String get playbackSpeed => '倍速';
+
   @override
   String minutesAgo(int count) {
     return '$count 分钟前';