GHSA-6mj3-qw4j-hgrw: xmldom: HTML raw-text closing-tag case mismatch causes output amplification

## Summary In HTML mode (`text/html`), a raw-text element (`script`, `style`, `textarea`, `title`) whose closing tag differs in case from its opening tag (e.g. ` ` for ` `) is mishandled by the parser, producing quadratic (O(n²)) output growth — a small crafted document parses and serializes into output orders of magnitude larger, exhausting CPU and memory. A modest input of tens of KB can therefore cause a denial of service in any service that parses untrusted HTML with xmldom. Only HTML mode is affected. …