Add related project: Document GPT

I've created a `document GPT`(chatPDF) which is based on "`langchain`" and "`gpt4free`".

The project initially utilized the Langchain to invoke the OpenAI model for implementing document GPT.

Now, it offers the option to use the gpt4free model, coupled with Hugging Face embedding.

**This integration enables users to use the document GPT app completely free**, without the need to input any API keys!

The [link](https://github.com/Lin-jun-xiang/docGPT-streamlit) has been added.

README.md

@@ -306,6 +306,13 @@ if __name__ == "__main__":
       <td><a href="https://github.com/Lin-jun-xiang/action-translate-readme/issues"><img alt="Issues" src="https://img.shields.io/github/issues/Lin-jun-xiang/action-translate-readme?style=flat-square&labelColor=343b41"/></a></td>
       <td><a href="https://github.com/Lin-jun-xiang/action-translate-readme/pulls"><img alt="Pull Requests" src="https://img.shields.io/github/issues-pr/Lin-jun-xiang/action-translate-readme?style=flat-square&labelColor=343b41"/></a></td>
     </tr>
+    <tr>
+      <td><a href="https://github.com/Lin-jun-xiang/docGPT-streamlit"><b>Langchain Document GPT</b></a></td>
+      <td><a href="https://github.com/Lin-jun-xiang/docGPT-streamlit/stargazers"><img alt="Stars" src="https://img.shields.io/github/stars/Lin-jun-xiang/docGPT-streamlit?style=flat-square&labelColor=343b41"/></a></td>
+      <td><a href="https://github.com/Lin-jun-xiang/docGPT-streamlit/network/members"><img alt="Forks" src="https://img.shields.io/github/forks/Lin-jun-xiang/docGPT-streamlit?style=flat-square&labelColor=343b41"/></a></td>
+      <td><a href="https://github.com/Lin-jun-xiang/docGPT-streamlit/issues"><img alt="Issues" src="https://img.shields.io/github/issues/Lin-jun-xiang/docGPT-streamlit?style=flat-square&labelColor=343b41"/></a></td>
+      <td><a href="https://github.com/Lin-jun-xiang/docGPT-streamlit/pulls"><img alt="Pull Requests" src="https://img.shields.io/github/issues-pr/Lin-jun-xiang/docGPT-streamlit?style=flat-square&labelColor=343b41"/></a></td>
+    </tr>
   </tbody>
 </table>
 
@@ -394,4 +401,4 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 <a href="https://github.com/xtekky/gpt4free/stargazers">
         <img width="500" alt="Star History Chart" src="https://api.star-history.com/svg?repos=xtekky/gpt4free&type=Date">
-</a>
+</a>