Rewrite docs URLs to remove .html

[Nutomic]

Would make it look a bit nicer.

[dessalines]

I checked, and it doesn't have those now.

[Nutomic]

Yes it does, eg http://jointest.lemmy.ml:1234/docs/introduction.html. Needs to be fixed in nginx config most likely.

[dessalines]

Ohhhh my bad, the docs ones.

Edit: to do that, we'd need to include an nginx layer, and a docker-compose.yml file for joinlemmy.

https://stackoverflow.com/questions/38228393/nginx-remove-html-extension