Add Get/Update Brotli setting

https://api.cloudflare.com/#zone-settings-get-brotli-setting

Add following in:

cloudflare-php/src/Endpoints/ZoneSettings.php

```PHP

public function GetBrotliSetting($zoneID)
{
$return = $this->adapter->get(
'zones/' . $zoneID . '/settings/brotli'
);
$body = json_decode($return->getBody());

if ($body->success) {
return $body->result->value;
}

return false;
}

public function updateBrotliSetting($zoneID, $value)
{
$return = $this->adapter->patch(
'zones/' . $zoneID . '/settings/brotli',
[
'value' => $value,
]
);
$body = json_decode($return->getBody());

if ($body->success) {
return true;
}

return false;
}

```

Thanks