PhpWeasyPrint vulnerable to arbitrary file deletion at shutdown via public $temporaryFiles

PhpWeasyPrint is a PHP library allowing PDF generation from a URL or an HTML page. Prior to version 2.6.0, `AbstractGenerator::$temporaryFiles` is a public array, and `removeTemporaryFiles()` — invoked from `__destruct()` and from a registered shutdown function — calls `unlink()` on every entry without verifying that the path is contained within the temporary folder. Any code holding a reference to a generator instance can push an arbitrary path into the array and have it deleted on script shutdown. This mirrors the KnpLabs/snappy issue GHSA-87qc-37cw-84h4. PhpWeasyPrint version 2.6.0 contains a patch for the issue.