Update guides and root project configurations

[ap0nia]

Objective

• Make the READMEs more concise and informative, especially for new members.
• Clean up the project's various configuration files so they adhere to a good standard.

README

• [ ] Table of Contents.
• [x] README at the project root will have general information for getting setup with developing in the repository. It will point to separate guides for the frontend and backend projects.

Configuration

• [x] Prefer JS and TS config files.
• [x] JS config files have the @ts-check directive to enable TypeScript checking on them.
• [x] Ignore files have more information about the types of files being ignored and why.
• [x] Move the LICENSE file to the project root.