GHSA-MJ63-M3RC-8PPR league/commonmark: Denial of service via deeply nested XML output

Impact XmlRenderer pretty-prints XML by emitting depth-proportional indentation whitespace for every opening and closing tag. For a tree of depth n, the indentation alone sums to On² bytes of output and corresponding memory, reachable through MarkdownToXmlConverter — e.g. strrepeat' ', $depth...