Add examples for min/max width/height.

docs/examples/styles/max_height.py

@@ -0,0 +1,16 @@
+from textual.app import App
+from textual.containers import Horizontal
+from textual.widgets import Placeholder
+
+
+class MaxHeightApp(App):
+    def compose(self):
+        yield Horizontal(
+            Placeholder("max-height: 10w", id="p1"),
+            Placeholder("max-height: 999", id="p2"),
+            Placeholder("max-height: 50%", id="p3"),
+            Placeholder("max-height: 10", id="p4"),
+        )
+
+
+app = MaxHeightApp(css_path="max_height.css")