docs: update diagram options

docs/diagram.md

@@ -51,3 +51,19 @@ with Diagram("Simple Diagram", show=False):
     EC2("web")
 ```
 
+If you are familiar with Graphviz, you can customize the diagrams with Graphviz attribute config options.
+
+> `graph_attr`, `node_attr` and `edge_attr` are allowed. Here is a [reference link](https://www.graphviz.org/doc/info/attrs.html).
+
+```python
+from diagrams import Diagram
+from diagrams.aws.compute import EC2
+
+graph_attr = {
+	"fontsize": 45,
+  "bgcolor": "transparent"
+}
+
+with Diagram("Simple Diagram", show=False, graph_attr=graph_attr):
+    EC2("web")
+```