Starterkit is a new custom theme creation process and base theme to replace Classy in Drupal 10.
It provides a new way of theming for Drupal.
Currently, it’s in alpha, but is on track to be stable for Drupal 10.
Why Starterkit?
While creating a theme for Drupal 8 or 9, the best practice was to subtheme the Classy core theme to ensure common CSS classes and the usual markup needed.
Thus it was imperative to call the Classy theme at runtime regardless of whichever custom theme you were using.
This dependency hindered the code updates on the Classy theme as any update would break backward compatibility.
As a result, Since Drupal 8.0.0, Classy has not been receiving updates.
Starterkit can help to solve this problem.
