Refactor DI container for better structure and clarity

- Moved `TSinjex` class to `classes` directory for better organization.
- Updated imports across the codebase to reflect the new location of `TSinjex`.
- Introduced `Identifier` type to standardize dependency identifiers.
- Enhanced JSDoc comments for improved clarity and consistency.
- Adjusted error messages for `DependencyResolutionError` to provide clearer information.
- Updated and expanded decorator and function types to use `Identifier` type.

src/index.ts

@@ -1,5 +1,5 @@
 // Main
-export * from './TSinjex';
+export * from './classes/TSinjex';
 
 // Decorators
 export * from './decorators/Inject';