Enhance JSONSchema documentation and visibility of types

[1amageek]

Description:

This pull request introduces the following improvements to the JSONSchema class:

1. Detailed Documentation:

   • Added comprehensive comments to the JSONSchema class and its components.
   • Describes features, usage, and the supported schema types.

2. Public Accessors:

   • Made the SchemaType enum public, enabling external access to supported schema types.
   • Added public properties type and description for the JSONSchema class, providing external visibility to the schema's type and description.

3. Enhanced Enum Definition:

   • Updated SchemaType with support for Codable and Sendable.

Changes:

• Improved documentation for JSONSchema and SchemaType:

  /// A class that represents a JSON Schema definition.
  ///
  /// `JSONSchema` is a flexible representation of a JSON Schema. It supports multiple schema types,
  /// including arrays, booleans, enums, integers, nulls, numbers, objects, and strings. The schema
  /// includes detailed metadata and type-specific information.
  ///
  /// ## Features
  /// - Supports various schema types.
  /// - Provides detailed descriptions for schema elements.
  /// - Implements `Codable` and `Sendable` for serialization and concurrency safety.
  public final class JSONSchema: Codable, Sendable {
      /// Enumeration of the supported JSON Schema types.
      public enum SchemaType: String, Codable, Sendable {
          case array
          case boolean
          case `enum`
          case string
      }
  
      /// The type of the schema.
      public let type: SchemaType
  
      /// An optional description providing additional information about the schema.
      public let description: String?
  }