feat(渲染能力): 优化字体名称识别，修复字体误回退

ofdgo_shading.go

@@ -22,6 +22,7 @@ import (
 	"github.com/tdewolff/canvas"
 )
 
+// shdPaint 渐变画刷
 type shdPaint struct {
 	gradient canvas.Gradient
 	view     canvas.Matrix