How to publish Slack app using Rails

My friend nudged me to build a Slack app that shares what's currently playing on Spotify to Slack channel. For a couple of days, I have put the finishing touches on it from nothing.This is my first time the Slack app built it done having in public although I had some for private workspace before. Only developing it is not enough you ought to submit it to Slack App Directory. Once passed it you would have completed done it.I'm writing about how to start off building a Slack app on Ruby on Rails and end up it has been in Slack App Directory.