Put back marketing chapter
Add section stub on custom domains
Merge branch 'new-release-edits' into marketing
Merge branch 'new-release-edits' into marketing
Merge branch 'new-release-edits' into marketing
Improve title
added content to marketing chapter + screenshots
added note about hide_custom_domain_footer
Update to latest gem
Update docs for new preview method
Merge branch 'marketing'

* marketing:
  Update docs for new preview method
  Update to latest gem
  added note about hide_custom_domain_footer
  added content to marketing chapter + screenshots
  Improve title
  Add section stub on custom domains
  Put back marketing chapter