how to verify signature in laravel

Hi, I wanted to know, I have a laravel project, and tried to implement this package in order to support payments with crypto.

The only problem I have is that I don't know how can I verify coinbase's signature on the webhook events.

What I'm trying to do is something like this example from the readme file:

```
use CoinbaseCommerce\Webhook;

try {
Webhook::verifySignature($signature, $body, $sharedSecret);
echo 'Successfully verified';
} catch (\Exception $exception) {
echo $exception->getMessage();
echo 'Failed';
}
```

I don't have any problem getting the signature or the shared secret, but I don't know how can I get the raw body of the request.

If anyone can help, I'd really appreciate it.

I'm using the following:
- PHP 8.0.10
- Laravel 8.61.0
- coinbase/coinbase-commerce: "^1.0",

Start with the README webhook example and Laravel 8.61.0 request handling, focusing on how the raw request body is obtained for the signature check. Done means documenting a Laravel-compatible way to provide the raw body to Webhook::verifySignature using the existing signature and shared secret.

Written by the indexing model from the issue text.