feat(game): play confetti for finished games

README.md

@@ -37,6 +37,9 @@ To Be Played is split into three repositories:
   a link to the game's speedrun.com page when it has verified runs, a hint when Steam shows recent playtime for a
   game still in the backlog, and one to set the status to 100 % when
   every achievement is unlocked.
+- **Confetti**: opening a finished game plays a small confetti burst, a finished game with every achievement a big
+  one; setting the status to finished plays it at once. Logo and accent colors, a canvas of our own (no library),
+  nothing with "reduce motion".
 - **Finished?**: Core marks a game as finished by itself when the ending achievement is unlocked and the status was
   never set by hand. Otherwise the game page asks: "You unlocked the ending, finished?" or "You played longer than
   most players need, finished?", with "Mark as finished" and "Not yet".