I’m interested in improving the Mail Configuration section by making it clear that, in development, to do things like Magic Link, you need to have something as MailHog configured.
It may sound silly but I’m pretty sure it will save people’s time 
But I’m not sure how to collaborate as long as I can’t find the repository that holds the docs
I had this same question and the official answer is to post your Docs suggestion here, in this forum. About the Contributing to Ghost category - #4 by RyanF
Here’s an example of what I did, although I haven’t heard back from the Ghost team yet…I think this is a down-side of their decision not to open-source the Docs, because rather than Pull Requests, you get this confusion and threads stay open for weeks without comments: Docs Suggestion: Clarify pre-requisites in "Install from Source"
Suggestion: Allow logging in as a seeded User locally - #4 by vanm
Judging by the questions in here, I think a lot of people care about good documentation, but it seems to be slipping through the cracks.