It would definitely be nice if there were a widget for this. But until then, there are a few ways you can approach this problem:
1) easiest, if the text is static, is to just use one 3D Label for each line of text
2) if the text is not static, you could use some Javascript code to take a string, work out the line breaks, and assign each line to its own 3D Label widget
3) You can also use Javascript to dynamically generate an SVG graphic (which is just XML under the hood) and assign it to a 3D Image widget
