Defines a CSS stylesheet for the document. Multiple "<style>" elements may be defined in a single document, and the aggregate document style is computed from that using CSS cascading rules.

Stylesheets support CSS Level 3: https://www.w3.org/TR/css-syntax-3/

DOM object: SVGStyleElement
SVG2 spec: https://www.w3.org/TR/SVG2/styling.html#StyleElement

<style>
  .myRect { fill: red; stroke: black; stroke-width: 2px; }
  circle { fill: black }
  circle:nth-child(2n) { fill: green }
</style>

Attribute	Default	Description
`type`	`text/css`	Type of the stylesheets contents, currently only `text/css` is supported.
`media`	(empty)	[unsupported] Specifies a media query that must be matched for the style sheet to apply.
`title`	(empty)	[unsupported] Specifies a title for the style sheet, which is used when selecting between alternate style sheets.

Note that type is defined to be a media type [rfc2046].