Update CopilotKit link in README.md

Author: NathanTarbert

README.md

@@ -138,7 +138,7 @@ AG-UI was born from CopilotKit's initial partnership with LangGraph and CrewAI -
 
 | Client | Status | AG-UI Resources | Integrations |
 | --- | ------- | ---------------- | ------------- |
-| [CopilotKit]() | ✅ Supported | ➡️ [Getting Started](https://docs.copilotkit.ai/direct-to-llm/guides/quickstart) | 1st Party |
+| [CopilotKit](https://github.com/CopilotKit/CopilotKit) | ✅ Supported | ➡️ [Getting Started](https://docs.copilotkit.ai/direct-to-llm/guides/quickstart) | 1st Party |
 | [Terminal + Agent]() | ✅ Supported | ➡️ [Getting Started](https://docs.ag-ui.com/quickstart/clients) | Community |
 | [React Native]() | 🛠️ Help Wanted | ➡️ [GitHub Source](https://github.com/ag-ui-protocol/ag-ui/issues/510) | Community |