Docs: Add hypergraph example with edge weights to visualize_graph usage section

Author: silkspace

README.md

@@ -118,7 +118,7 @@ The main tool, `visualize_graph`, now accepts a single `graph_data` dictionary.
 ```python
 {
   "graph_data": {
-    "data_format": "edge_list",
+    "graph_type": "graph",
     "edges": [
       {"source": "A", "target": "B"},
       {"source": "A", "target": "C"},
@@ -140,6 +140,25 @@ The main tool, `visualize_graph`, now accepts a single `graph_data` dictionary.
 }
 ```
 
+Example (hypergraph):
+
+```python
+{
+  "graph_data": {
+    "graph_type": "hypergraph",
+    "edges": [
+      {"source": "A", "target": "B", "group": "G1", "weight": 0.7},
+      {"source": "A", "target": "C", "group": "G1", "weight": 0.6},
+      {"source": "B", "target": "C", "group": "G2", "weight": 0.8},
+      {"source": "A", "target": "D", "group": "G2", "weight": 0.5}
+    ],
+    "columns": ["source", "target", "group"],
+    "title": "Test Hypergraph",
+    "description": "A simple test hypergraph."
+  }
+}
+```
+
 ### What We Learned / Caveats & Gotchas
 
 - **Environment Variables & .env:** Always ensure `GRAPHISTRY_USERNAME` and `GRAPHISTRY_PASSWORD` are set in the environment or `.env` file. The server loads `.env` automatically using `python-dotenv`.