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/risk_of_rain_2/egg-risk-of-rain2.json

@@ -8,7 +8,9 @@
     "name": "Risk of Rain 2",
     "author": "alex.chang-lam@protonmail.com",
     "description": "Risk of Rain 2 dedicated server.",
-    "features": null,
+    "features": [
+        "steam_disk_space"
+    ],
     "images": [
         "quay.io\/parkervcp\/pterodactyl-images:debian_wine-5"
     ],
@@ -83,4 +85,4 @@
             "rules": "required|numeric"
         }
     ]
-}
+}