Support filled beziercurve rendering

[goccy]

resolve #24

The following codes outputs expected results.

package main

import (
	"context"

	"github.com/goccy/go-graphviz"
)

func main() {
	if err := _main(context.Background()); err != nil {
		panic(err)
	}
}

func _main(ctx context.Context) error {
	g, err := graphviz.New(ctx)
	if err != nil {
		return err
	}

	graph, err := g.Graph()
	if err != nil {
		return err
	}
	a, err := graph.CreateNodeByName("a")
	if err != nil {
		return err
	}
	b, err := graph.CreateNodeByName("b")
	if err != nil {
		return err
	}
	if _, err := graph.CreateEdgeByName("e", a, b); err != nil {
		return err
	}

	a.SetStyle(graphviz.WedgedNodeStyle)
	a.SetShape(graphviz.EllipseShape)
	a.SetFillColor("blue:red:yellow")

	b.SetShape(graphviz.BoxShape)
	b.SetStyle(graphviz.StripedNodeStyle)
	b.SetFillColor("blue:red:yellow")

	if err = g.RenderFilename(ctx, graph, graphviz.PNG, "test.png"); err != nil {
		return err
	}
	return nil
}