function textElRadius(textEl, minR, step) {
	const farthestPoint = svgTxtFarthestPoint(textEl);
	return ceil(minR, step, Math.sqrt(farthestPoint.x ** 2 + farthestPoint.y ** 2));
}
calc radius that cover all <tspan> in SVGTextElement
origin is in the center of the circle
@param {SVGTextElement} textEl
@param {*} minR
@param {*} step