refactor: major overhaul of project structure and entry points

[Tony133]

Proposal:

This PR represents a significant refactoring of the project structure to align with modern standards and improve maintainability.

Structural Changes:

• Moved core logic from src/ to a more standard lib/ directory.
• Decoupled tests from the source files by moving them from src/*.test.js to a dedicated top-level test/ directory.
• Created a root index.js to serve as the official entry point, replacing the internal references to src/.
• Extracted src/example.js into a proper examples/ directory.
• Standardized TypeScript definitions into types/index.d.ts and types/index.tst.ts.

Improvements:

• Better separation between library logic, tests, and documentation/examples.
• Simplified the package distribution by having clear, standard entry points.
• Developer Experience: Improved the ease of navigation within the repository.

Note:

• New project structure:

fluent-json-schema/
├── examples/              
│   └── examples.js
├── lib/                   
│   ├── ArraySchema.js
│   ├── BaseSchema.js
│   ├── BooleanSchema.js
│   ├── FluentJSONSchema.js
│   ├── IntegerSchema.js
│   ├── MixedSchema.js
│   ├── NullSchema.js
│   ├── NumberSchema.js
│   ├── ObjectSchema.js
│   ├── RawSchema.js
│   ├── StringSchema.js
│   ├── utils.js
│   └── schemas/
│       └── basic.json
├── test/                  
│   ├── ArraySchema.test.js
│   ├── BaseSchema.test.js
│   ├── ...
│   ├── FluentSchema.integration.test.js
│   └── utils.test.js
├── types/                
│   ├── index.d.ts        
│   └── index.tst.ts     
├── index.js               
├── package.json         
├── tsconfig.json        
└── README.md