Version 1.1.3 fails in browser - Buffer is not defined

We wanted to use the package to create hashes in Chrome, but on initial testing it seems like this package doesn't work in the browser.

When attempting to import the package it fails with the error message:

```
Buffer is not defined
```

You can see an minimal example in this Code Sandbox:
https://codesandbox.io/s/x2xyrq2plp

从最小的 CodeSandbox 复现和 createHash 中的包导入路径开始。在 Chrome 中确认失败，然后追踪浏览器 bundle 对 Buffer 的依赖；当该包能够导入并在 Chrome 中创建哈希，且不出现“Buffer is not defined”时，即视为完成。

由索引模型根据 Issue 内容生成。