Adding Postgres as a supported consumer

[hashanwcreately]

[hashanwcreately]

Add Postgres support to Siddi event tracking system

• Integrate Postgres as a new event consumer
• Add pgConfig.ts for Postgres connection configuration
• Modify siddi.ts:
  • Add postgresClient property
  • Implement initPostgres method for connection setup
  • Update close method to handle Postgres connection
• Update consumers.ts:
  • Add Postgres consumer with test, identify, and track methods
  • Implement robust connection testing for Postgres
• Ensure backward compatibility with existing consumers
• Add necessary type declarations for global Postgres client

This commit enables Siddi to store events and user data in a Postgres
database while maintaining support for existing event consumers.