Add CSS property `caret-shape` and shorthand `caret`

[BarryCap]

The CSS caret-shape (where we can set auto | bar | block | underscore) and the shorthand caret (combining attributes of caret-color and caret-shape) should be added, even though at the time this is written and to my knowledge, they are not supported by any browser.

Links and information

• caret W3C specification
• caret-color W3C specification
• caret-shape W3C specification
• Bugzilla on caret-shape implementation (bug 1715487)
• CSS-Tricks article on caret (by Geoff Graham)
• CSS-Tricks article on caret-color (by Chris Coyier)
• CSS-Tricks article on caret-shape (by Geoff Graham)
• Stack Overflow question on CSS caret styling