how to target older browsers with Bun.build?

[giladgray]

I am interested in converting a sizable Webpack (CRA) app to Bun.build and Bun.serve but one requirement is being able to down-level syntax to ensure that it's compatible with our target browsers, which is basically Chrome >= 79: not terribly old but not super fresh. Unfortunately, Babel is really good at this.

I see this small note in the first row of the table in https://bun.sh/docs/bundler#content-types:

At the moment Bun does not attempt to down-convert syntax; if you use recently ECMAScript syntax, that will be reflected in the bundled code.

How would I go about integrating a tool to down-convert syntax in my build? Is there a plugin I can use or a reliable fast library for which I could write my own plugin? My ideal would be to define settings in tsconfig.json like target and module and have the system go from there.