feat: add Together AI integration and provider implementation guide

- Create detailed provider implementation guide with:
  - Architecture overview and implementation steps
  - Configuration patterns and best practices
  - Testing checklist and Docker integration guide
  - Example using Together AI implementation
- Add Together AI as new provider with:
  - Environment variables and Docker configuration
  - Support for Qwen, Llama, and Mixtral models
  - API key and base URL management
  - OpenAI-compatible API integration

.env.example

@@ -38,12 +38,18 @@ OLLAMA_API_BASE_URL=
 # You only need this environment variable set if you want to use OpenAI Like models
 OPENAI_LIKE_API_BASE_URL=
 
+# You only need this environment variable set if you want to use Together AI models
+TOGETHER_API_BASE_URL=
+
 # You only need this environment variable set if you want to use DeepSeek models through their API
 DEEPSEEK_API_KEY=
 
 # Get your OpenAI Like API Key
 OPENAI_LIKE_API_KEY=
 
+# Get your Together API Key
+TOGATHER_API_KEY=
+
 # Get your Mistral API Key by following these instructions -
 # https://console.mistral.ai/api-keys/
 # You only need this environment variable set if you want to use Mistral models