Mention how to write docs for public Mix tasks
Mention how to write docs for public Mix tasks

You have to write a @moduledoc in order to show some documentation when
users do `mix help my_task`.

joshprice/elixir,kimshrier/elixir,ggcampinho/elixir,ggcampinho/elixir,kelvinst/elixir,beedub/elixir,kelvinst/elixir,lexmag/elixir,gfvcastro/elixir,antipax/elixir,pedrosnk/elixir,lexmag/elixir,gfvcastro/elixir,antipax/elixir,beedub/elixir,kimshrier/elixir,pedrosnk/elixir,michalmuskala/elixir,elixir-lang/elixir