Include class summary as comment

[FH-Inway]

Nice project, my first experiments with it were successful. #167 was a timely addition, as policy fragments are my main interest for this at the moment.

Playing around with it, I added functionality to include the class summary as a comment in the xml file. For example, this

using Microsoft.Azure.ApiManagement.PolicyToolkit.Authoring;

namespace Microsoft.Azure.ApiManagement.PolicyToolkit.Example;

/// <summary>
/// Fragment: auth-fragment
/// 
/// Purpose: Add basic authentication headers
/// </summary>
[Document("auth-fragment", Type = DocumentType.Fragment)]
public class AuthenticationFragment : IFragment
{
    public void Fragment(IFragmentContext context)
    {
        context.SetHeader("X-Auth-Fragment", "true");
        context.AuthenticationBasic("{{username}}", "{{password}}");
    }
}

would become this

<!-- This file is generated by the Azure API Management Policy Toolkit -->
<!-- Version: 1.0.0.0 -->
<!--
    Fragment: auth-fragment
    
    Purpose: Add basic authentication headers
    -->
<fragment>
  <set-header name="X-Auth-Fragment" exists-action="override">
    <value>true</value>
  </set-header>
  <authentication-basic username="{{username}}" password="{{password}}" />
</fragment>

If there is interest in adding this, I would work on it some more and start a pull request.