Migrate contrib module Style Switcher's old doc page into new doc guide

As described in https://www.drupal.org/drupalorg/docs/content/documentation#migrate I’m opening this issue to ask for help with:

I’ve already copied the body of the doc and updated it a little, so no other tasks are needed except the 2 above.

P.S.: I don’t see other issues of the same purpose here in the documentation issue queue, and I couldn’t find any info about what should I set in this issue’s metadata. I guess it’d be better to provide some template or at least some info in issue submission guidelines.

Source: https://www.drupal.org/project/issues/rss/documentation