feat: add Google Gemini provider integration and docs

src/index.ts

@@ -29,12 +29,14 @@ export { BaseAIProvider } from './providers/base.js';
 // Concrete provider implementations
 export { ClaudeProvider, type ClaudeConfig } from './providers/claude.js';
 export { OpenAIProvider, type OpenAIConfig } from './providers/openai.js';
+export { GeminiProvider, type GeminiConfig } from './providers/gemini.js';
 
 // Utility functions and factory
 export {
   createProvider,
   createClaudeProvider,
   createOpenAIProvider,
+  createGeminiProvider,
   ProviderRegistry,
   type ProviderType,
   type ProviderConfigMap
@@ -51,4 +53,4 @@ export const VERSION = '1.0.0';
 /**
  * List of supported providers
  */
-export const SUPPORTED_PROVIDERS = ['claude', 'openai'] as const; 
+export const SUPPORTED_PROVIDERS = ['claude', 'openai', 'gemini'] as const;