Response description

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

As far as i can see there is no way to provide a description to a response type. The standard `.Produce` methods don't have any parameter for it, and I've even tried this with no luck -
```csharp
.WithOpenApi(operation =>
{
operation.Responses["200"].Description = "Downloadable HTML file containing all todos in a formatted table";
operation.Responses["204"].Description = "No todos available to export";
return operation;
})
```
and
```csharp
.WithMetadata(new ProducesResponseTypeMetadata(StatusCodes.Status200OK, null, ["text/html"]) { Description = "Downloadable HTML file containing all todos in a formatted table" })
```

### Describe the solution you'd like

An extra parameter added to the `.Produces` method to add the description field

### Additional context

Looks like currently internally it populates it with the response status code name. Ideally, we should be able to override it or append to it