Add basic support for indented sass

[antonyfaris]

Fixes #9
This is a temporarily fix until a SASS prettier plugin is made available.
The content of the style tag won't be indented.
The output will be like this:

<style lang="sass">
$bg: #1E1E1E
$text: #9cdcfe
$shadow: #0002
$fonts: monaco, Consolas, 'Lucida Console', monospace

body
  padding: 0
  margin: 0
  background: $bg

.header
  background: lighten($bg, 2.5)
  box-shadow: 0 1px 4px $shadow
  justify-content: center
</style>

Instead for this:

<style lang="sass">
  $bg: #1E1E1E
  $text: #9cdcfe
  $shadow: #0002
  $fonts: monaco, Consolas, 'Lucida Console', monospace

  body
    padding: 0
    margin: 0
    background: $bg

  .header
    background: lighten($bg, 2.5)
    box-shadow: 0 1px 4px $shadow
    justify-content: center
</style>

[drwpow]

Very nice! Clean implementation, too. I don’t have any feedback other than “this looks great!”