Add Facebook username validation functionality

[Ronak501]

This pull request introduces a new function for validating Facebook usernames in the user_scanner/social/facebook.py file. The main change is the addition of logic to check if a Facebook username exists, is available, or if an error occurred during the validation process.

New Facebook username validation functionality:

• Added the validate_facebook function, which checks the existence of a Facebook username by analyzing HTTP responses and URL patterns, returning codes for available, unavailable, or unknown/error states.
• Implemented error handling for connection and timeout exceptions using httpx to ensure robust network requests.

Command-line interface:

• Added a simple CLI for testing the function, allowing users to input a username and receive feedback on its availability.

[kaifcodec]

@Ronak501 Thanks for the PR but the validator might have some issues, I tested it locally.

If you are free enough, take your time and open a new PR again with cleaner approach and following the new CONTRIBUTING guidelines.

Anyways there was an unwanted file named uv.lock which I think you might have pushed accidentally, I deleted that file.

Thanks for putting your efforts to user-scanner.