feat: add custom node class (#25)

* feat: add custom node class

* docs: add example about custom node

* docs: improve example about custom node usage

* docs: fix variable name

diagrams/custom/__init__.py

@@ -0,0 +1,20 @@
+"""
+Custom provides the possibility of load an image to be presented as a node.
+"""
+
+from diagrams import Node
+
+
+class Custom(Node):
+    _provider = "custom"
+    _type = "custom"
+    _icon_dir = None
+
+    fontcolor = "#ffffff"
+
+    def _load_icon(self):
+        return self._icon
+
+    def __init__(self, label, icon_path):
+        self._icon = icon_path
+        super().__init__(label)

docs/getting-started/examples.md

@@ -169,3 +169,34 @@ with Diagram("Stateful Architecture", show=False):
 ```
 
 ![stateful architecture diagram](/img/stateful_architecture_diagram.png)
+
+## RabbitMQ Consumers with custom nodes
+
+```python
+from urllib.request import urlretrieve
+
+from diagrams import Cluster, Diagram
+from diagrams.custom import Custom
+from diagrams.aws.database import Aurora
+from diagrams.k8s.compute import Pod
+
+# Download an image to be used into a Custom Node class
+rabbitmq_url = "https://jpadilla.github.io/rabbitmqapp/assets/img/icon.png"
+rabbitmq_icon = "rabbitmq.png"
+urlretrieve(rabbitmq_url, rabbitmq_icon)
+
+
+with Diagram("Broker Consumers", show=False):
+    with Cluster("Consumers"):
+        consumers = [
+            Pod("worker"),
+            Pod("worker"),
+            Pod("worker")
+        ]
+
+    queue = Custom("Message queue", rabbitmq_icon)
+
+    queue >> consumers >> Aurora("Database")
+````
+
+![rabbitmq consumers diagram](/img/rabbitmq_consumers_diagram.png)