"--" in domain story breaks SVG

[hofstef]

Describe the bug
If two minus characters ("--") are used anywhere in the domain story (title, description, labels, annotation), the SVG export will be broken.
The reason is that the SVG file contains an embedded EGN file as comment:

<!-- <DST>
  {
     (domain story as JSON)
  }
</DST> -->

If the JSON contains "--", SVG viewers will interpret this as closing tag of the comment. The rest of the comment is interpreted as SVG content and hence leads to an error when the viewer tries to render it.

Version

• Egon: v2.0.0-2.2.0