Playtime+

Adds a simple clock showing how long the current game has been running.

Compare to the original playtime:
- Better performance (update only once per 60 ticks)
- Custom positioning by mod setting page or mouse dragging
- Right click to reset position
- Dark theme

Note that the time is in-game time not a real time. For instance, the time is calculated by the total number of ticks passed (60 ticks = 1 second).