Nanotrasen Block Game is here (#2131)

* tetris!

* softdropping & left,right key holding

* started work on the ui

* playable state

* there you go exp

* multiuser rework

* ui update refactor

* blockgame™️

* highscores, keybindings, ui refactor

* speed adjusts
leveling

* highscorebackground tweak
speed tweak

* NULLABLE

* yes

Content.Shared/Arcade/BlockGameUiKey.cs

@@ -0,0 +1,11 @@
+using System;
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.Arcade
+{
+    [Serializable, NetSerializable]
+    public enum BlockGameUiKey
+    {
+        Key
+    }
+}