Issue #922696 by mgifford, EvanDonovan, LewisNyman, stpaultim, jensimmons: New...

Issue #922696 by mgifford, EvanDonovan, LewisNyman, stpaultim, jensimmons: New methods, standards for describing core themes on themes admin page (was Theme screenshots do not have adequate alt text...).

core/themes/stark/stark.info.yml

 name: Stark
 type: theme
-description: 'This theme demonstrates Drupal''s default HTML markup and CSS styles. To learn how to build your own theme and override Drupal''s default code, see the <a href="http://drupal.org/theme-guide">Theming Guide</a>.'
+description: 'An intentionally plain theme with almost no styling to demonstrate default Drupal’s HTML and CSS. Learn how to build a custom theme from Stark in the <a href="http://drupal.org/theme-guide">Theming Guide</a>.'
 package: Core
 version: VERSION
 core: 8.x