JS app in /web/a/ (exclude from wp rewrite)

I have a backbone.js app in Bedrock’s web folder (/site/web/a/). How can i exclude it from Wordpress rewrite rules? This should be pretty simple on Apache & htaccess, but not sure how to do it on this custom nginx setup.
Would it be a better approach to create another site within the same trellis setup, just for the js app?