[css-cascade-3] [editorial] Please add "Changes since 2.1"

[tantek]

This is requested for the next draft to go to CR, to make it easier for web authors and developers who are familiar with CSS 2.1 to understand what CSS3 Cascade adds and changes.

Please add "Changes since 2.1" to https://drafts.csswg.org/css-cascade-3/#changes
that lists at a minimum:

New Features:

• 'all' property
• ... anything else?

New terminology:

• The ... and ... values are new in [css-cascade-3]

Changes to existing terminology:

• The ... and ... values were changed from 2.1

New algorithms:

• The algorithms for determining ... and ... are changed from 2.1

Thanks!