Adding JSX to list of languages

_Disclsocure: This is a plug for my own mode_

Would it be possible to add JSX as its own language in the selection pane, including [`rjsx-mode`](https://github.com/felipeochoa/rjsx-mode) as the package to use for it? `rjsx` extends `js2` to add syntax highlighting for JSX -- no config needed beyond just `use-package`. You could just use the [React logo](https://github.com/facebook/react/blob/master/docs/img/logo.svg), which is [CC BY 4.0 licensed](https://github.com/facebook/react/blob/master/LICENSE-docs)