extra: readability mode about downstyler

[waldyrious]

quick & dirty:

html {
  background: grey;
}

body {
  background: white;
  max-width: 40em;
  padding: 1em 5em;
  margin: 10px auto;
  border-radius: 2px;
  text-align: justify;
}

[waldyrious]

This should be a separate style (using @include, perhaps?) with its own bookmarklet, or maybe a bookmarklet that applies both unstyle.css and the rules above.