Port Custom Dojo Middleware blog post from learn-dojo

Port https://learn-dojo.com/dojo-custom-middleware/ over to dojo site, and update any parts where necessary to make sure the content is current. We might also want to make this more generic in the introduction of it also ie, how to use and create middleware.

Make sure the blog post is authored by whoever picks this up and Rene Rubalcava, with a cross-link at the bottom back to the original post.

Start by reading the original custom middleware post at https://learn-dojo.com/dojo-custom-middleware/ and locate the corresponding blog content in the dojo site. Compare the material for currentness, broaden the introduction to cover using and creating middleware where appropriate, and verify the author attribution and cross-link to the original post.

Written by the indexing model from the issue text.