[suggestion] Add ctor to ReseEase that allow to add both RequestModifier and HttpMessageHandler

[Legion-ale]

Discussed in https://github.com/canton7/RestEase/discussions/231

^{Originally posted by Legion-ale July 21, 2022} As explained in the title i'm in the following situation:

private readonly Microsoft.Extensions.Http.PolicyHttpMessageHandler retryPolicyHandler = new Microsoft.Extensions.Http.PolicyHttpMessageHandler(
	Policy.HandleResult<HttpResponseMessage>(r => r.StatusCode == System.Net.HttpStatusCode.BadGateway)
			.RetryAsync()
);

private readonly RequestModifier proxyHandler = async (request, cancellationToken) =>
{
	//Lot of code to set some proxy stuff before sending the call
};

But when i try to inizialize RestEase i cannot add both to the ctor (even if i use new RestClient(...)) and i need to choose only one of the 2 following ctors: RestClient.For<IWebApi>(API_URL, proxyHandler); (ctor that accept RequestModifier) RestClient.For<IWebApi>(API_URL, retryPolicyHandler); (ctor that accept HttpMessageHandler) There are not public members that allow me to edit that configuration in a second time because HttpClient is a private property (as it should be).

Thanks and sorry for my bad english :) L-