SVG export generates invalid XML, when escaping emojis

[YorikHansen]

When exporting a rendered graph to svg, emojis are not escaped to their codepoints. Instead the SVG contains the escaped bytes (which results in invalid XML).

Example:
👩🏾‍💻 (Woman Technologist: Medium-Dark Skin Tone) gets escaped to ����‍�� but it should either stay 👩🏾‍💻 or get escaped to it's codepoints 👩🏾‍💻 (Woman + Medium-Dark Skin Tone + Zero Width Joiner + Laptop).

KGT-file (added .txt suffix to please github): example-issue-222.kgt.txt
SVG-file:

[NiklasRentzCAU]

For a little context: This issue occurs in the FreeHEP SVG exporter and is caused by the text normalization found in the XMLWriter class. This code has not been maintained in years, though.
A workaround could be implemented in the SemanticsSVGGraphics2D class in the writeString method, also taken from FreeHEP. Feel free to suggest improvements. Currently, the method is given the String
ߑ©ߏ¾‍ߒ»
for that emoji and the 7 bytes seem to come from that.
For comparison: The new SVG export by using klighd-vscode correctly renders the emoji in the SVG, albeit a little squished because AWT does not correctly estimate the size of the emoji.