LibWeb: Tracking issue for Filter Effects 1 specification

[ADKaster]

Uses of filter effects elements and functions in the wild include github.com's not-logged-in homepage.

https://drafts.fxtf.org/filter-effects-1/

Changes include:

• [ ] the "filter" property (https://drafts.fxtf.org/filter-effects-1/#FilterProperty)
• [ ] SVGFilterElement (https://drafts.fxtf.org/filter-effects-1/#FilterElement)
• [ ] All the filter primitives (feColorMatrix, feBlend, feGaussianBlur ...)