Choose how fast the world timeline plays

A speed menu beside play offers real time, an hour, a day or a week a
second, a day a second to start with. A speed chosen while playing applies
at once; chosen while weather's own replay steps its frames, it takes
playback over from where it is. Play starts again from the top only at live
or at the very end, so a pause just before the end plays on. On phones the
menu sits beside the track, a full-size target.

src/i18n/locales/zh-CN.json

@@ -2871,5 +2871,9 @@
   "Right panels": "右侧面板",
   "World time": "世界时间",
   "Back to live": "返回实时",
-  "Live": "实时"
+  "Live": "实时",
+  "1 h/s": "1 小时/秒",
+  "1 d/s": "1 天/秒",
+  "1 wk/s": "1 周/秒",
+  "Play speed": "播放速度"
 }