creates index-file for a given folder to expose everthing inside
npm install js-indexer --save-dev
./node_modules/.bin/js-indexer ./src/components/index.js ./src/utils/index.ts
./node_modules/.bin/js-indexer --filter 'index\.js' ./src/components/index.js ./src/utils/index.ts
test-files and files with leading _
will be excluded.