Serve raw markdown files by appending .md extension to url

[ozziexsh]

👋 Hey, this adds the ability to append .md to a url to receive the raw markdown format for easier LLM usage, e.g.

/docs/installation.md

It would be great to have a general /llms.txt with an index of all the pages, as well as a copy as markdown on each page too but I don't have time for that just yet :) I can open another PR in the future if that is something you'd consider adding

I also couldn't get playwright to run locally (even though its working with pest 4 in other repos locally) so not sure if the test is passing, though I verified it works when serving the application itself and visiting the urls