feat: support multi-line labels

diagrams/__init__.py

@@ -260,6 +260,8 @@ class Node:
     _icon_dir = None
     _icon = None
 
+    _height = 1.9
+
     def __init__(self, label: str = ""):
         """Node represents a system component.
 
@@ -272,9 +274,11 @@ class Node:
         # fmt: off
         # If a node has an icon, increase the height slightly to avoid
         # that label being spanned between icon image and white space.
+        # Increase the height by the number of new lines included in the label.
+        padding = 0.4 * (label.count('\n'))
         self.attrs = {
             "shape": "none",
-            "height": "1.9",
+            "height": str(self._height + padding),
             "image": self._load_icon(),
         } if self._icon else {}
         # fmt: on