Add CORS Middleware to playground-mono for Enhanced Security and Flexibility

[rishavvajpayee]

Implement Cross-Origin Resource Sharing (CORS) middleware in the playground-mono backend to control which domains can access API resources. This will enhance security and allow flexible configurations for different environments

1. Create a CORS middleware in the middleware package: • Allow specific origins by setting Access-Control-Allow-Origin based on the environment configuration. • Include headers for allowed methods and allowed headers. • Handle OPTIONS requests with a proper 200 OK response.

2. Update LoadConfig() in the config package to support the new ALLOWED_ORIGINS configuration: • Parse a comma-separated string from an environment variable into a slice of strings.

3. Add CORS to all applicable routes in the main.go file or route initialization

[iRittikSharma]

@lucifercr07 I would like to work on this issue could you please assign it to me

[rishavvajpayee]

related PR : https://github.com/DiceDB/playground-mono/pull/13

[lucifercr07]

Closing, merged as part of https://github.com/DiceDB/playground-mono/pull/13