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/the_forest/egg-the-forest.json

@@ -8,7 +8,9 @@
     "name": "The Forest",
     "author": "admin@softwarenoob.com",
     "description": "As the lone survivor of a passenger jet crash, you find yourself in a mysterious forest battling to stay alive against a society of cannibalistic mutants. Build, explore, survive in this terrifying first-person survival horror simulator.",
-    "features": null,
+    "features": [
+        "steam_disk_space"
+    ],
     "images": [
         "ghcr.io\/parkervcp\/yolks:wine_latest"
     ],
@@ -137,4 +139,4 @@
             "rules": "required|boolean"
         }
     ]
-}
+}