Add a quickstart guide to documentation

For new users transitioning to `crypto-browserify` (for example due to recent [`create-react-scripts 5` breakage](https://github.com/facebook/create-react-app/pull/11764)), it would be really helpful if the user guide had a small example of how to:

- Install `crypto-browserify` and configure `package.json`
- How to import and use the package

For example, treating this like a normal `npm` package, I expected that this could work:

```json
"dependencies": {
"crypto-browserify": "^3.12.0",
```

```ts
import hash from "crypto-browserify";
```

But it does not. Likely this needs to be patched over the `"crypto"` namespace, but having explicit instructions for this would be helpful.