Add DDraceNetwork

The game is a Teeworlds modification that outgrown the original game.
- It has more devs and more players
- It has own Steam page
- It provides a different gameplay.

code/archives.json

@@ -657,6 +657,7 @@
   "https://github.com/davidjoffe/dave_gnukem.git",
   "https://github.com/db0/godot-card-game-framework.git",
   "https://github.com/ddevault/TrueCraft.git",
+  "https://github.com/ddnet/ddnet.git",
   "https://github.com/deathbeam/spooker.git",
   "https://github.com/deathbeam/yae.git",
   "https://github.com/deathkiller/jazz2.git",