[ISSUE-44] Refactor .envs for Scripts

[LuisValgoi]

Description

This PR refactors the .env variables to consider mock and start

Dependency

N/A

Config

Are you adding a configuration file?

• Have you updated the publish scripts?

Are you adding a new feature

• [ ] Have you updated the README.md?

Testing

• yarn mock to see it running
• yarn start will require an available API

Automated Tests

• [ ] Select this if your code has automated Tests for it.

References

• Add & Fix yarn start w/ backend #44