test: add genCalc test.

Author: YumoImer

src/index.ts

@@ -1 +1,4 @@
-export { default as genStyleUtils } from './util/genStyleUtils';
+export { default as genStyleUtils } from './util/genStyleUtils';
+
+export { default as genCalc } from './util/calc';
+export type { default as AbstractCalculator } from './util/calc/calculator';