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/barotrauma/egg-barotrauma.json

@@ -8,7 +8,9 @@
     "name": "Barotrauma",
     "author": "admin@softwarenoob.com",
     "description": "Barotrauma is a 2D co-op survival horror submarine simulator, inspired by games like FTL: Faster Than Light, Rimworld, Dwarf Fortress and Space Station 13. It\u2019s a Sci-Fi game that combines ragdoll physics and alien sea monsters with teamwork and existential fear.",
-    "features": null,
+    "features": [
+        "steam_disk_space"
+    ],
     "images": [
         "ghcr.io\/parkervcp\/games:source"
     ],
@@ -47,4 +49,4 @@
             "rules": "required|string|max:20"
         }
     ]
-}
+}