How to target subdirectories in BuckleScript bsconfig.json

I have the following folder structure

--| button
--|--| button.re
main.re

In my bsconfig.json, using the quickstart guide found here. I have in my config the following key/value:

"sources": [
  "src/"
]

It is only targeting the main.re file. I have tried some conventional config options such as *.re, but to no avail. If I would like to target all sub-directories, how would I do so? Thank you.