Update USAGE.md
Update USAGE.md

When I tried using just "react.js" this in a Play project I got this error:
JSLibResolveException: Some references to JS libraries could not be resolved:
- Ambiguous reference to a JS library: react.js
Possible paths found on the classpath:
- META-INF/resources/webjars/react/0.12.2/vendor/fbtransform/transforms/react.js
- META-INF/resources/webjars/react/0.12.2/react.js
originating from: client:compile
Specifying the more specific path solved it.
beni55/scalajs-react,japgolly/scalajs-react,zlangbert/scalajs-react,beni55/scalajs-react,matthughes/scalajs-react,zlangbert/scalajs-react,7thsense/scalajs-react,matthughes/scalajs-react,japgolly/scalajs-react,beni55/scalajs-react,CodeMettle/scalajs-react,japgolly/scalajs-react,matthughes/scalajs-react,japgolly/scalajs-react,CodeMettle/scalajs-react,7thsense/scalajs-react,CodeMettle/scalajs-react,zlangbert/scalajs-react,7thsense/scalajs-react