docs: update readme.md

Author: yeonjuan

README.md

@@ -26,6 +26,12 @@ See [online demo](https://yeonjuan.github.io/parse-git-diff/)
 
 ## Usage
 
+```js
+import parseGitDiff from 'parse-git-diff'; // import
+// or
+const parseGitDiff = require('parse-git-diff').default; // require
+```
+
 ```js
 import parseGitDiff from 'parse-git-diff';