No/Wrong instructions on sh into the container on readme.md

[dotslash21]

Overview

Following the readme.md on setting up the repo for development in my local machine, while sh-ing into the container using $ docker exec -it <container-id> /bin/sh doesn't work. The main cause for this is .env.sample which on yarn start produces an error and the container exits immediately with error code 1. The readme.md needs to be updated with the necessary instructions to build, run and debug the docker container on local environments.