Add Factory Method for Flexible Rate Limiting Policy Configuration

[neelp03]

Description:
Implement a factory method that allows users to dynamically choose and configure rate-limiting policies. This will improve flexibility in the selection of rate-limiting algorithms and their parameters.

Acceptance Criteria:

• Implement the factory method in ratelimiter to support dynamic policy configuration.
• Provide configuration for all existing policies (Fixed Window, Sliding Window, Token Bucket, Leaky Bucket).
• Add unit tests to validate the factory method behavior.
• Update examples and documentation to show how the factory method works.