fix: using export type to re-exporting for isolatedModules is enabled

Author: thekiba

index.ts

@@ -1,5 +1,5 @@
 export { generateCode, getTLBCode, getTLBCodeByAST, generateCodeByAST, generateCodeWithGenerator, generateCodeFromData } from "./src/main";
 export * from "./src/ast";
 export { isBigInt as isBigIntForJson, isBigIntExpr as isBigIntExprForJson } from "./src/generators/typescript/utils";
-export { CodeGenerator } from "./src/generators/generator";
-export { TypescriptGenerator } from "./src/generators/typescript/generator";
+export type { CodeGenerator } from "./src/generators/generator";
+export { TypescriptGenerator } from "./src/generators/typescript/generator";