Feature request: add or update <title> child node

[apiontek]

Thanks for this module, it works great and is really useful.

For accessibility & hover-text, a <title> tag inside an <svg> is very useful. It can be set in the .svg files ahead of time, but I've encountered several cases where it would be preferable to vary the <title> inner text. To that end, it'd be a great additional feature to be able to provide an attr to update or insert the top-level <title> node, something like:

<.svg name="backspace" title_tag="Clear input" />

Resulting in something like:

<svg ...><title>Clear input</title>...</svg>

And if the SVG already contains a <title> it should replace it.