Add support to insert a new language to kirikiri scn script

src/types.rs

@@ -503,6 +503,9 @@ pub struct ExtraConfig {
     /// Workers count for packing file in Kirikiri XP3 archive in parallel. Default is 1.
     /// This not works when segment is disabled.
     pub xp3_pack_workers: usize,
+    #[cfg(feature = "kirikiri")]
+    /// Insert new language at the specified index in Kirikiri SCN script. If index is out of bounds, this flags will be ignored.
+    pub kirikiri_language_insert: bool,
 }
 
 #[derive(Clone, Copy, Debug, ValueEnum, PartialEq, Eq, PartialOrd, Ord)]