extensions/emmet/src/util.ts/isStyleAttribute
export function isStyleAttribute(currentNode: FlatNode | undefined, offset: number): boolean {
	if (!currentNode) {
		return false;
	}
	const currentHtmlNode = <HtmlFlatNode>currentNode;
	const index = (currentHtmlNode.attributes || []).findIndex(x => x.name.toString() === 'style');
	if (index === -1) {
		return false;
	}
	const styleAttribute = currentHtmlNode.attributes[index];
	return offset >= styleAttribute.value.start && offset <= styleAttribute.value.end;
}