(fix): fix CJS for entries that are in subdirs of src/

- use fs.outFile to mkdirp the equivalent subdirectory in dist/ if it
  didn't exist before

src/index.ts

@@ -535,7 +535,7 @@ if (process.env.NODE_ENV === 'production') {
 }
 `;
   const filename = numNames === 1 ? 'index.js' : `${name}.js`;
-  return fs.writeFile(path.join(paths.appDist, filename), contents);
+  return fs.outputFile(path.join(paths.appDist, filename), contents);
 }
 
 function getAuthorName() {