getReactNativeVersion = (context = {}) => {
  const version = getVersionFromContext(context)
  return is(String, version) ? version : REACT_NATIVE_VERSION
}
Gets the React Native version to use.

Attempts to read it from the command line, and if not there, falls back
to the version we want for this boilerplate.  For example:

  $ npx ignite-cli new Custom --react-native-version 0.61.1

@param {*} context - The gluegun context.