fix: change template to work with jest (facebook#23150)

Summary:
This change is required to make `yarn test` work in newly initialized project.
`Jest@23` doesn't play well with new babel, so we need to install `babel-core@^7.0.0-bridge.0` and change `.babelrc` to `babel.config.js` to make it work. This is a temporary change till `jest` releases stable `24` version.
Pull Request resolved: facebook#23150

Differential Revision: D13811428

Pulled By: hramos

fbshipit-source-id: 8db6b9177cd31d4a1213fb44964b05f26982bdf2

Author: Esemesek

template/_babelrc

@@ -0,0 +1,3 @@
+module.exports = {
+  presets: ['module:metro-react-native-babel-preset'],
+};