Widen config search paths to include metro.config.cjs (#1027)

Summary:
Pull Request resolved: #1027

Resolves #1026.

Changelog: **[Feature]** Widen config search paths to include `metro.config.cjs`

Reviewed By: robhogan

Differential Revision: D47290079

fbshipit-source-id: 3e46c954a1e1451558b14ed4558fede5f00200dd

packages/metro-config/src/loadConfig.js

@@ -46,13 +46,18 @@ function overrideArgument<T>(arg: Array<T> | T): T {
 }
 
 const explorer = cosmiconfig('metro', {
- searchPlaces: ['metro.config.js', 'metro.config.json', 'package.json'],
-
+ searchPlaces: [
+ 'metro.config.js',
+ 'metro.config.cjs',
+ 'metro.config.json',
+ 'package.json',
+ ],
  loaders: {
  '.json': cosmiconfig.loadJson,
  '.yaml': cosmiconfig.loadYaml,
  '.yml': cosmiconfig.loadYaml,
  '.js': cosmiconfig.loadJs,
+ '.cjs': cosmiconfig.loadJs,
  '.es6': cosmiconfig.loadJs,
  noExt: cosmiconfig.loadYaml,
  },