Tell the user that it takes a long time to initialize a new project

[eschnett]

When I created a new project via haskell-do, the indicator on the web page kept spinning for several minutes. I finally gave up.

Please add an indication that things can take VERY long initially (ten minutes?), and/or add a better progress indicator. stack build, by default, produces progress output -- I assume you hide it on purpose? Not good.

[NickSeagull]

Thanks for opening an issue @eschnett ! When opening creating a new project a message saying "Downloading dependencies" should be rendered, isnt that the case for you? 😄