code: function setEnv(constants) {
    const setter = context => prevConfig => {
      context.setEnv = Object.assign({}, context.setEnv, toObject(constants))
      return prevConfig
    }
  
    return Object.assign(setter, { post: addEnvironmentPlugin })
  }
docs: Replaces constants in your source code with values from `process.env`
  using the `webpack.EnvironmentPlugin`.
  
  Using `setEnv` multiple times results in a single
  EnvironmentPlugin instance configured to do all the replacements.
  
  @param {string[]|object} constants
  @return {Function}