title: Automatic Dependency Management with stack such as `stack add <module>`
body: <p>it there a command to tell <code>stack</code> to add a dependency in the cabal file? I think of a convenient way like with <code>npm</code> or <code>yarn</code> (<code>npm install &lt;module&gt; --save</code>, <code>yarn add &lt;module&gt;</code>). I think it is a bit tedious to manually add a new module in die cabal file. Maybe this functionality could automatically include version information as well.</p>
  
  <p>I know that a cabal file has different targets, so it is not as easy as with <code>npm</code> or <code>yarn</code>. But I think it would be useful.</p>
  
  <p>Thanks :)</p>