docs: enhance PostgreSQL documentation with advanced features

[amanluthra001]

• Add transaction handling examples
• Include join operations and complex queries
• Add prepared statements for better performance
• Include migration examples and connection pool configuration

[Umang01-hash]

@amanluthra001 again you have created a new file inside docs/features. This is not the place where the existing documentation of MySQL exists. It lies here. Please make the changes here. Also you don;t need to create the documentation from raw as stated earlier you can modify and add things to existing one.

[amanluthra001]

@amanluthra001 again you have created a new file inside docs/features. This is not the place where the existing documentation of MySQL exists. It lies here. Please make the changes here. Also you don;t need to create the documentation from raw as stated earlier you can modify and add things to existing one.

I have made the reqd changes . Can u pls check