docs: update demo iframe height and add Gradio app integration

docs/en/demo.md

@@ -1 +1,4 @@
-<iframe src="https://opendatalab-mineru.hf.space" frameborder="0" width="850" height="450"></iframe>
+<iframe src="https://opendatalab-mineru.hf.space" frameborder="0" width="850" height="850"></iframe>
+
+<script type="module" src="https://gradio.s3-us-west-2.amazonaws.com/5.35.0/gradio.js"></script>
+<gradio-app src="https://opendatalab-mineru.hf.space"></gradio-app>