Add alternative Use extension method to MarkdownPipelineBuilder that receives an object instance

[augustoproiete]

This PR adds an overload of the MarkdownPipelineBuilder.Use<T> method that receives an instance of an IMarkdownExtension, for the cases where the extension has a constructor requiring parameters and cannot be instantiated by the existing Use<T> method.

Syntax looks like this:

var pipeline = new MarkdownPipelineBuilder()
	.Use(new MyAwesomeExtension("param1", "param2")) // <== here
	.UseAdvancedExtensions()
	.Build();

[xoofx]

Thanks!