Add Prettier linting instructions to `CONTRIBUTING.md`.

[HarshKapadia2]

• File to be changed: CONTRIBUTING.md
• We need to inform contributors that we have a linting check in place.
  • This can be added as a note below the 'Tech Stack' section.
    • Eg: > NOTE: This repository has a Prettier code linting CI check. Please follow the Prettier instructions mentioned below.
• We also need to inform contributors that they need to use Prettier before committing and provide instructions to do so.
  • Instructions should be provided for each type of environment, the Gitpod Setup and the Local Setup.
  • Instructions should be pertaining to how Prettier can be added/installed and which commands to execute or what method to follow to use Prettier.

Credits: @tusharnankani (in a PR comment)

[KartikSoneji]

Also mention how to enable the pre-commit hook if they want to as per #126

[HarshKapadia2]

A good video to understand and set up Prettier: https://www.youtube.com/watch?v=DqfQ4DPnRqI

[tusharnankani]

Thank you, this helped!