fix: add src export default

.tool-versions

@@ -1 +1 @@
-nodejs 12.18.4
+nodejs 14.15.3

src/index.ts

@@ -1,3 +1,5 @@
 import { MathMLToLaTeX } from './main';
 
+export default MathMLToLaTeX;
+
 module.exports = MathMLToLaTeX;