Fix bgi script import bug

src/scripts/bgi/parser.rs

@@ -214,6 +214,12 @@ pub enum BGIStringType {
     Internal,
 }
 
+impl BGIStringType {
+    pub fn is_internal(&self) -> bool {
+        matches!(self, BGIStringType::Internal)
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct BGIString {
     pub offset: usize,