Tracking: SVG support

[nicoburns]

SVG Support

Blitz currently has basic support for SVGs referenced via <img src> and inline <svg> elements. This support is based on the usvg and anyrender_svg crates.

• Version of usvg based on fontations
• Custom SVG rendering using Blitz's DOM (should enable animations)

[yisibl]

usvg currently uses simplecss for CSS parsing. Due to its overly simplified architecture, it appears unable to keep pace with the evolving CSS syntax. If usvg is selected for adoption, this issue must be resolved first.