vscode-xml: XSD download fails in recent versions

I noticed that this extension no longer downloads external schemas for me. I’m behind a corporate proxy.

This is part of my settings.json: "xml.server.vmargs": "-Dhttp.proxyHost=PROXYHOST -Dhttp.proxyPort=3128 -Dhttps.proxyHost=PROXYHOST -Dhttps.proxyPort=3128"

The last working extension version is 0.9.1 (downgrading does the trick for me). 0.10.0 and 0.10.1 are broken for me.

This is the error I get:

{
	"resource": "/c:/Users/pfliegel.sebastian/Projects/MDS/src/main/db/tables/changelog_20200220.xml",
	"owner": "_generated_diagnostic_collection_name_#0",
	"severity": 8,
	"message": "Error while downloading 'http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.8.xsd' to C:\\Users\\pfliegel.sebastian\\.lsp4xml\\cache\\http\\www.liquibase.org\\xml\\ns\\dbchangelog\\dbchangelog-3.8.xsd.",
	"source": "XML",
	"startLineNumber": 3,
	"startColumn": 2,
	"endLineNumber": 3,
	"endColumn": 19
}

This issue is similar to #134, but I assume only the proxy settings were missing (as only more recent versions are affected by this bug).