title: @fluent-ui/react vs @fluent-ui/react-northstar
body: <p>I'm looking for some guideline what's the difference between <strong>@fluent-ui/react</strong> and <strong>@fluent-ui/react-northstar</strong>. This documentation (READMEs) are super imprecise. I'm don't understand which one to use for what.
  I'm writing that react-component to be ran in webapp and the word plugin. Do you know which one to go for? They both look a bit different and feels that theming works a bit different.</p>