Add optional reject cookie support with explicit consent state

[Numair25]

This PR proposes adding support for a "Reject" option alongside the existing "Allow cookies" functionality.

It is based on a discussion opened here: #208

Summary of changes:

• Adds a "Reject" button in the dialog
• Stores consent state in the same cookie:
  • 1 = accepted
  • 0 = rejected
• Treats both values as a decision, so the banner does not reappear
• Maintains backward compatibility by continuing to rely on cookie existence

This allows developers to distinguish between accepted and rejected users and conditionally load scripts based on consent.

Happy to adjust or align with the package direction if needed.

[freekmurze]

I'm going to keep the package a simple as possible for now.