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/project_zomboid/egg-project-zomboid.json

@@ -8,7 +8,9 @@
     "name": "Project Zomboid",
     "author": "iamkubi@gmail.com",
     "description": "Project Zomboid is an open world survival horror video game in alpha stage development by British and Canadian independent developer, The Indie Stone. The game is set in a post apocalyptic, zombie infested world where the player is challenged to survive for as long as possible before inevitably dying.",
-    "features": null,
+    "features": [
+        "steam_disk_space"
+    ],
     "images": [
         "ghcr.io\/pterodactyl\/games:source"
     ],
@@ -101,4 +103,4 @@
             "rules": "required|string|max:20"
         }
     ]
-}
+}