Implement `MultiValueHeaders` for ``events.LambdaFunctionURLResponse``

**Is your feature request related to a problem? Please describe.**
The `events.LambdaFunctionURLResponse` doesn't support `MultiValueHeaders` which became in come use. For now, the workaround is to set up the APIGatewayv2 instance and use `events.APIGatewayV2HTTPResponse`, which sometimes doesn't provide an economic reason to use APIGatewayv2 just for small Lambda.

**Describe the solution you'd like**
I would like to ask you to implement `MultiValueHeaders` support for `events.LambdaFunctionURLResponse`, bellow you can check the structure example:

```go
type LambdaFunctionURLResponse struct {
StatusCode int `json:"statusCode"`
Headers map[string]string `json:"headers"`
MultiValueHeaders map[string][]string `json:"multiValueHeaders"`
Body string `json:"body"`
IsBase64Encoded bool `json:"isBase64Encoded"`
Cookies []string `json:"cookies"`
}
```

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**
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