quickjs [1] has native support for Cosmopolitan, is meant to be easily embeddable, and is included as part of the standard Cosmopolitan distribution. It looks like qjs also has patches for recent-ish versions of the Typescript compiler as well. Someone has made a nodejs-style project called txiki.js [2] using vanilla qjs. Maybe it would build with Cosmopolitan with some tweaking. But if you're thinking of packaging a whole browser engine like Electron that might be a Sisyphian effort.

[1] https://bellard.org/quickjs/ [2] https://github.com/saghul/txiki.js/