Support custom project directory.

[X-W-W]

I set project sourceDir in react-native.config.js, but it's not in use.

Here is my react-native.conf.js
module.exports = { project: { ios: { sourceDir: "./apps/mobile/ios", }, android: { sourceDir: "./apps/mobile/android", } }, assets:[ "./assets/fonts" ] }

now it just seek root path ./ios and ./android
node_modules\react-native-asset\lib\get-config.js
const iosPath = path.resolve(rootPath, 'ios'); const androidPath = path.resolve(rootPath, 'android');