[Chore] Add database and Redis setup instructions to the README

[olivierobert]

Issue

While the README has detailed information on how you have approached the technical challenge of scraping, following the instructions were not sufficient to run the application. I need to have both Postgres and Redis running and running the Rails command to set up the Postgres database and run the migration.

Expected

The README file must contain all the required information for developers to set up the application in their local environments. So the following pieces of information are required: Ruby / Node versions and database(s) setup.

Note Using Docker compose to set up the database services would make the project setup easier.

[olivierobert]

The updates in #19 are a good improvement 👍