Fix/142 xlinkhref is deprecated

[luukbrauckmann]

Changes

• Adds href to the use element. Kept xlink:href as fallback.
• Also adds some suggestions for improving accessibility.

Associated issue

Resolves #142

How to test

1. Run dev server
2. Check share link
3. Icon works 🎉

Checklist

• [x] I have performed a self-review of my own code
• [x] I have made sure that my PR is easy to review (not too big, includes comments)
• [ ] ~I have made updated relevant documentation files (in project README, docs/, etc)~
• [ ] ~I have added a decision log entry if the change affects the architecture or changes a significant technology~
• [x] I have notified a reviewer

[luukbrauckmann]

Added some accessibility improvements. I think this would be a better way than the previous version. If someone disagrees then I'm curious why.

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