addConfigTransform (key, options) {
    const hasReserved = Object.keys(this.generator.reservedConfigTransforms).includes(key)
    if (
      hasReserved ||
      !options ||
      !options.file
    ) {
      if (hasReserved) {
        const { warn } = require('@vue/cli-shared-utils')
        warn(`Reserved config transform '${key}'`)
      }
      return
    }

    this.generator.configTransforms[key] = new ConfigTransform(options)
  }
Configure how config files are extracted.

@param {string} key - Config key in package.json
@param {object} options - Options
@param {object} options.file - File descriptor
Used to search for existing file.
Each key is a file type (possible values: ['js', 'json', 'yaml', 'lines']).
The value is a list of filenames.
Example:
{
  js: ['.eslintrc.js'],
  json: ['.eslintrc.json', '.eslintrc']
}
By default, the first filename will be used to create the config file.