Enable serving of static Markdown content to JavaScript running on any domain

AllowMarkdownCorsModule.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace MyWebsite.Helpers
{
    public class AllowMarkdownCorsModule : IHttpModule
    {
        public void Init(HttpApplication context)
        {
            context.BeginRequest += BeginRequestHandler;
        }
    
        private void BeginRequestHandler(object sender, EventArgs e)
        {
            HttpApplication application = (HttpApplication)sender;
            HttpContext context = application.Context;
            string filePath = context.Request.FilePath;
            string fileExtension = VirtualPathUtility.GetExtension(filePath);
            if (fileExtension?.ToLower() == ".md")
            {
                context.Response.AddHeader("access-control-allow-origin", context.Request.Headers["origin"]);
                if (context.Request.Headers["access-control-request-headers"] != null)
                {
                    context.Response.AddHeader("access-control-allow-headers", context.Request.Headers["access-control-request-headers"]);
                }
                context.Response.Cache.SetCacheability(HttpCacheability.Public);
                context.Response.Cache.SetMaxAge(TimeSpan.FromSeconds(3600));
                context.Response.Cache.SetExpires(DateTime.UtcNow.AddSeconds(3600));
            }
        }
    
        public void Dispose()
        {
            
        }
    }
}

web.config

<configuration>
  <system.webServer>
    <modules>
      <add name="MarkdownAllowCorsModule" type="MyWebsite.Helpers.AllowMarkdownCorsModule" />
    </modules>
    <staticContent>
      <remove fileExtension=".md" />
      <mimeMap fileExtension=".md" mimeType="text/markdown" />
    </staticContent>
  </system.webServer>
</configuration>