Add in-app guidance (e.g. getting started tutorial, tips and tricks)

[kollivier]

While there is documentation for the app, many apps these days walk you through getting started in the app itself, by showing you where key features are in the interface, and how to use them. This would significantly improve the getting started experience.

Tips and tricks should similarly be "just in time", meaning they are displayed when they are relevant to a user. For example, if a user is writing a really long article, a tip icon might appear, and when expanded it may suggest breaking down the article, putting some information into "more information" links, adding some multimedia, etc.