Add COLRv1 color font rendering support

Adds a ColorRenderer that renders COLR v0/v1 glyphs via skrifa's
ColorPainter trait and tiny-skia as the 2D backend. Each glyph is
rendered once and cached as an RGBA tile; subsequent uses composite
the cached tile. The existing outline renderer is unchanged and used
for non-color fonts via an if/else dispatch in diff_many_words.

Author: m4rc1e

Cargo.lock

@@ -39,6 +39,7 @@ unicode_names2 = "0.6.0"
 brotli = "6.0.0"
 lazy_static = "1.4.0"
 zeno = "0.3.1"
+tiny-skia = "0.12"
 log = "0.4"
 
 static-lang-word-lists = { version = "0.3.0", features = ["rayon"] }