fix: fixed the throw error when the dist folder don't exist

src/webpack-mjml-store.js

@@ -174,7 +174,7 @@ WebpackMjmlStore.prototype.readFile = function (file) {
     try {
       fs.readFile(file, 'utf8', function (err, data) {
         if (err) {
-          throw err;
+          resolve(true);
         }
         resolve(data);
       });