Add title to SvgOptions

[matbech]

It would be nice if the SvgOptions class adds an optional 'title' property. If set, the title would then be added as a child of the rect element:

<rect ... fill="#ffffff">
  <title>title</title>
</rect>

The title will be shown as a tooltip when the mouse hovers over the element. See:
https://developer.mozilla.org/en-US/docs/Web/SVG/Element/title
demo:
https://stackoverflow.com/questions/10643426/how-to-add-a-tooltip-to-an-svg-graphic