…ive-stylesheet-urls

* 'develop' of github.com:ampproject/amp-wp: (962 commits)
  Fix hasChanges/hasSaved logic in unsaved changes warning
  Update assets/src/setup/components/unsaved-changes-warning/index.js
  Use *.snap instead of __snapshots__ in .gitattributes
  Add beforeunload listener only after changes
  Set version option to readonly
  JS doc param fix
  Remove unnecessary checks
  Set linguist-generated for Jest snapshots
  Setup wizard: Update screen titles
  Fix issue with setup wizard mobile width
  Add unsaved changes warning message
  Skip broken test that needs fix upstream
  Only use 'all and...' in conjunction with 'not'
  Keep selectors unsorted
  Fix CS in markup comparison helper
  Adapt ServerSideRendering transformer to make use of CssRule(s)
  Add CssRules collection class and tests
  Add CssRule class and tests
  Move attribute-order-agnostic comparison to assertSimilarMarkup()
  Normalize start tag attributes by sorting and squashing whitespace
  ...