gameStore: Added functions to add and retrieve games

[criticic]

Implemented the createGame function which creates a new game, generates it's id and adds it the the games map.

Also added the retrieveGame function which retrieves a game, given it's id.

Also added the uuid package to generate unique ids for games.

Fixes #5

Screenshots and screen captures

Self-review checklist

• Self reviewed the changes for clarity and maintainability (variable names, code reuse, readability, etc.).
• Highlights technical choices and bugs encountered.
• Calls out remaining decisions and concerns.
• Automated tests verify logic where appropriate.
• Each commit is a coherent idea.
• Commit message(s) explain reasoning and motivation for changes.

Completed manual review and testing of the following:

• Visual appearance of the changes.
• End-to-end functionality of buttons, interactions and flows.
• Corner cases, error conditions, and easily imagined bugs.

[criticic]

Rebased on the recent commits