Docs: Add instructions for generating YouTube API Key in Frontend README

### Is this related to an existing part of the documentation?

- [x] Yes, it is related to an existing section

### What needs to be updated?

**📌 Current Documentation Issue**
The `Frontend/env-example` file requires a `VITE_YOUTUBE_API_KEY`, but the `Frontend/README.md` does not explain how to generate this key. New contributors setting up the project locally are stuck guessing how to obtain these credentials from the Google Cloud Console.

**✨ Proposed Changes**
I propose adding a dedicated section to `Frontend/README.md` that guides the user through:
1. Opening Google Cloud Console and creating credentials.
2. Enabling the "YouTube Data API v3".
3. Generating an API key and restricting it properly.
4. Adding the key to the `.env` file.

**📋 Additional Context**
I have just set up the project locally and can document the exact steps I took to get it working.

### Relevant Documentation Link (if any)

_No response_

### Record

- [x] I agree to follow this project's Code of Conduct
- [x] I want to work on this update