Support `xml.format.xsiSchemaLocationSplit` setting with experimental formatter

[angelozerr]

See https://github.com/redhat-developer/vscode-xml/blob/master/docs/Formatting.md#xmlformatxsischemalocationsplit

[angelozerr]

@JessicaJHee do you want to work on this issue?

[JessicaJHee]

Yes!