GHSA-4HGP-59H5-GVRJ ratex-parser panics on `\verb` with a multibyte delimiter (UTF-8 byte-boundary slice)

Summary The public parser entrypoint ratexparser::parse&str panics on the 9-byte input \verbéxé i.e. \verb followed by the non-ASCII delimiter é. When handling a \verb command, the parser slices the verbatim argument with byte indices arg1..arg.len - 1; if the delimiter character is multibyte...