feat: add steam_disk_space egg feature to SteamCMD eggs

A new egg feature modal was introduced in Panel v1.7.0 triggering when server has run out of disk space to provide more user-friendly instructions to both admins and normal users. This is unique to SteamCMD specific errors.

game_eggs/steamcmd_servers/subnautica_nitrox_mod/egg-subnautica.json

@@ -8,7 +8,9 @@
     "name": "Subnautica",
     "author": "tueye@tuworld.de",
     "description": "Subnautica is an open world survival action-adventure video game developed and published by Unknown Worlds Entertainment. In it, players are free to explore the ocean on an alien planet, known as planet 4546B, after their spaceship, the Aurora, crashes on the planet's surface.\r\n\r\nNote: NitroxMod version >=1.5.0.0 is required",
-    "features": null,
+    "features": [
+        "steam_disk_space"
+    ],
     "images": [
         "quay.io\/pterodactyl\/core:mono"
     ],
@@ -146,4 +148,4 @@
             "rules": "required|string|in:PROTOBUF,JSON"
         }
     ]
-}
+}