1.2.0 beta 2

Includes two updates since the first beta draft:

• Fixes for displaying pre-1.2.0 Critical CSS error information, and
• Cleans out unnecessary extra files from production repos.

1.2.0 Beta

Added

• Critical CSS: Added a new Advanced Critical CSS recommendations page.

Changed

• Critical CSS: Updated error reporting for Critical CSS to offer more users more guidance.
• Updated package dependencies.
• Tooling: Moved all development to the Jetpack monorepo.

Fixed

• Tooling: Fix PHP unit testing dependency on later versions of PHP.