Find out what exactly onlyNewElements does and add docs. If it

[todo]

goldst.github.io/js/mouseShadow/MouseShadowController.js

Lines 24 to 29 in 4a86c4b

	* @todo Find out what exactly onlyNewElements does and add docs. If it
	* doesn't do anything, delete it.
	* @returns {void}
	*/
	constructor(baseElement, blocks = [], queryFilter = '*', onlyNewElements = true) {
	super(baseElement, queryFilter, ['mouse-shadow-element', ...blocks.map(b => 'mouse-shadow-element-' + b)], onlyNewElements, ME);

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This issue was generated by todo based on a todo comment in 4a86c4b when #36 was merged. cc @goldst.