Support for SVG 2 - href attribute

[sanderd17]

Describe the bug When importing an external SVG, it gets imported as a "use" element with an xlink:href to the external SVG.

Although SVG 2 is in "Candidate Recommendation" state, MDN actively recommends against it ( https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/xlink:href ).

To Reproduce Steps to reproduce the behavior:

1. Import an external SVG, export the SVG string, see how "xlink:href" is used

OR

1. Set an SVG string with href attribute on a use element, watch how the element gets removed from the SVG

Expected behavior Exports should probably start exporting with href in the near future, and imports with href shouldn't fail.

SVG-Edit environment (IMPORTANT)

• File for SVG-Edit: direct JS manipulation
• Version: 4.1.0

Desktop (please complete the following information):

• OS: Linux
• Browser chrome, firefox
• Version 71, 64