Add links to headers in Markdown files

[aManNamedJed]

This is a plugin that we can just pull in that will automatically autolink the headers so that they are shareable like GitHub style. I would love to maybe someday not use a plugin for this as I think that we can maybe, but why re-invent the wheel here.

https://www.gatsbyjs.com/plugins/gatsby-remark-autolink-headers/