Make the second planet after Lignumis configurable by other mods

lignumis/settings.lua

@@ -54,6 +54,14 @@ data:extend({
         setting_type = "startup",
         default_value = false,
         order = "h"
+    },
+    {
+        type = "string-setting",
+        name = "lignumis-second-planet",
+        setting_type = "runtime-global",
+        allowed_values = { "nauvis" },
+        default_value = "nauvis",
+        hidden = true
     }
 })