paths like `/post/example-post` should serve `example-post.html`

[NathanRHD]

I actually think it's fairly standard practice outside of react or angular frameworks for paths like /post/example-post to go to example-post.html

This is a part of the modern web, I think.

If you look at the url for this pull request, for example, it is https://github.com/YunoHost-Apps/my_webapp_ynh/pull/76 without a file extension!

Originally posted by @NathanRussellUK in https://github.com/YunoHost-Apps/my_webapp_ynh/issues/76#issuecomment-1168559495