Intent to Implement and Ship: CSS inset/inset-block/inset-inline shorthands

Summary: The inset-block CSS property is a shorthand for the inset-block-start/end properties (ditto -inline). The 'inset' CSS property is a shorthand for the top, right, bottom, and left properties. Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1520229 Link to standard:

Intent to Implement and Ship: CSS border-{block,inline}-{color,style,width} and border-{block,inline} shorthands

Summary: The border-{block,inline}-{color,style,width} CSS properties are shorthand for their respective -start/-end properties. The border-{block,inline} are shorthand for their respective -start/-end shorthands, though you can only specify one value (which is used on both the -start/-end