update LaTeX parser

[mathjiajia]

Thanks for reporting a bug! Please include all of the following:

(1) A description of the issue. A screenshot is often helpful too. In a normal document, difft usually reports that there are xxx LaTeX parser errors. This is because the LaTeX parser is outdated.

(2) A copy of what you're diffing. If you're diffing files, include the before and after files. If you're using difftastic with a VCS repository (e.g. git), include the URL and commit hash.

(3) The version of difftastic you're using (see difft --version) and your operating system. Difftastic 0.58.0 (built with rustc 1.78.0), macOS