Add dom element as getter/setter

[uf0]

Why don't we manage the DOM element as other chart prop (data,etc) with getter/setter and avoid https://github.com/rawgraphs/rawgraphs-core/blob/api-experiments/src/raw.js#L111

const mychart = chart(visualModel, config, DOM_node)

[bianchimro]

Because other props can be just set with no side effects on the DOM, while "binding" to a DOM node happens when the chart is rendered to the node with renderToDom