Add pygwalker example (#2800)

Very simple example showing usage in marimo.

examples/third_party/pygwalker/example.py

@@ -0,0 +1,31 @@
+# /// script
+# requires-python = ">=3.10"
+# dependencies = [
+#     "pygwalker==0.4.9.13",
+#     "vega-datasets==0.9.0",
+# ]
+# ///
+import marimo
+
+__generated_with = "0.9.14"
+app = marimo.App(width="medium")
+
+
+@app.cell
+def __():
+    import pygwalker as pyg
+
+    from vega_datasets import data
+    return data, pyg
+
+
+@app.cell
+def __(data, pyg):
+    df = data.iris()
+
+    pyg.walk(df)
+    return (df,)
+
+
+if __name__ == "__main__":
+    app.run()