[css-?] Standardize text-stroke #4795

The prefixed -webkit-text-stroke, -webkit-text-stroke-color and -webkit-text-stroke-width properties are widely supported. They are currently defined in the Compatibility Standard. Browsers also support -webkit-text-fill which seems unnecessary because the color property can be used instead.

Should we standardize similar properties? Something like:

• text-stroke-color: <color> (initially currentcolor)
• text-stroke-width: <line-width> (initially medium like in border-width? Not 0 like in the compat spec)
• (maybe also?) text-stroke-offset: <length>
• text-stroke (a shorthand for the above properties)

[#963 (comment) refers to CSS Fill and Stroke Module, but it seems to only apply to SVG elements.]