Add OpenAPI-to-Application collections for 5 common frameworks

[shibicr93]

Add 5 framework-specific collections with shared agent and prompt for generating production-ready applications from OpenAPI specifications:

• Java Spring Boot
• Python FastAPI
• Node.js NestJS
• C# .NET
• Go

Reuses existing framework instructions for consistency and best practices.

Pull Request Checklist

• I have read and followed the CONTRIBUTING.md guidelines.
• My contribution adds a new instruction, prompt, or chat mode file in the correct directory.
• The file follows the required naming convention.
• The content is clearly structured and follows the example format.
• I have tested my instructions, prompt, or chat mode with GitHub Copilot.
• I have run npm start and verified that README.md is up to date.

---

Description

Add OpenAPI-to-Application collections that enable users to generate production-ready applications from OpenAPI specifications across multiple frameworks.

New Resources:

• Agent: openapi-to-application (generic framework-agnostic OpenAPI generator)
• Prompt: openapi-to-application-code (shared template for code generation)
• Collections (5):
  • openapi-to-application-java-spring-boot (Spring Boot)
  • openapi-to-application-python-fastapi (Python FastAPI)
  • openapi-to-application-nodejs-nestjs (Node.js NestJS)
  • openapi-to-application-csharp-dotnet (C# .NET)
  • openapi-to-application-go (Go)

Design:

• Reuses existing framework-specific instructions for consistency
• Generic agent and shared prompt reduce duplication

---

Type of Contribution

• New instruction file.
• New prompt file.
• New chat mode file.
• New collection file.
• New skill file.
• Update to existing instruction, prompt, chat mode, collection or skill.
• Other (please specify): New Agent

---

Additional Notes

All the collections are verified individually with the Petstore OpenAPI Spec

---

By submitting this pull request, I confirm that my contribution abides by the Code of Conduct and will be licensed under the MIT License.