Typemill has Reflected XSS via login error view template

Typemill is a flat-file, Markdown-based CMS designed for informational documentation websites. A reflected Cross-Site Scripting (XSS) exists in the login error view template `login.twig` of versions 2.19.1 and below. The `username` value can be echoed back without proper contextual encoding when authentication fails. An attacker can execute script in the login page context. This issue has been fixed in version 2.19.2.