x_labels line breaks

First I'd like to thank you for creating such a wonderful library/tool! However I was wondering if it's possible to have line breaks in the `x_labels`. Currently adding `\n` adds an actual line break in the SVG file which isn't rendered. I noticed this issue has been addressed with the `tooltips` but doesn't appear to be working for `x_labels`.

Thanks

Start by comparing the existing tooltip line-break handling with the x_labels rendering path, then inspect the generated SVG for a label containing a newline. The work is done when newline characters in x_labels render as visible line breaks rather than only creating a source-level line break in the SVG.

Written by the indexing model from the issue text.