Add steps for shadow-cljs build

Hey, this tool looks awesome. I'm new to clojure world (and build options are the most complex things in it 😅 ). Can you please add steps to integrate it with [shadow-cljs](https://shadow-cljs.github.io/docs/UsersGuide.html) (without add code modifications).

Start by reading the linked shadow-cljs user guide and the repository's existing integration documentation, though the issue does not name a documentation file. Add steps for integrating cljs-devtools with shadow-cljs without code modifications, and consider the work done when a reader can follow the documented setup successfully.

Written by the indexing model from the issue text.