feat(wizards): Pretty print XML inside code editor, closes #895

[danyill]

Closes #895

We use formatXml to save documents.

Is it dangerous to use it here? Perhaps a little bit.

When OpenSCD modifies elements e.g. datasets, subscriptions or supervision elements, the XML it produces is difficult to view in the Ace editor without manually adding linebreaks. This resolves that.

[Sander3003]

Let's try it, @danyill please check if private sections are still working with multiple vendors.

[ca-d]

LGTM, we decided at today's refinement that it would be nice to test this pretty printing on some real world vendor specific Private sections to see if changing whitespace presents a problem in that scenario

[danyill]

Thanks for reviewing. I will look into testing this, although it should be no less safe than our existing "Save Project".