path 绘制
<svg height="210" width="400">
<path d="M150,0 L75,200 L225,200 Z" style="fill:lime;stroke:purple;stroke-width:1" />
</svg>
polygon 绘制
<svg height="210" width="400">
<polygon points="150,0 75,200 225,200" style="fill:lime;stroke:purple;stroke-width:1" />
</svg>
