Add example for column-span.

docs/examples/styles/column_span.css

@@ -0,0 +1,30 @@
+#p1 {
+    column-span: 4;
+}
+#p2 {
+    column-span: 3;
+}
+#p3 {
+    column-span: 1;  /* Didn't need to be set explicitly. */
+}
+#p4 {
+    column-span: 2;
+}
+#p5 {
+    column-span: 2;
+}
+#p6 {
+    /* Default value is 1. */
+}
+#p7 {
+    column-span: 3;
+}
+
+Grid {
+    grid-size: 4 4;
+    grid-gutter: 1 2;
+}
+
+Placeholder {
+    height: 100%;
+}

docs/examples/styles/column_span.py

@@ -0,0 +1,19 @@
+from textual.app import App
+from textual.containers import Grid
+from textual.widgets import Placeholder
+
+
+class MyApp(App):
+    def compose(self):
+        yield Grid(
+            Placeholder(id="p1"),
+            Placeholder(id="p2"),
+            Placeholder(id="p3"),
+            Placeholder(id="p4"),
+            Placeholder(id="p5"),
+            Placeholder(id="p6"),
+            Placeholder(id="p7"),
+        )
+
+
+app = MyApp(css_path="column_span.css")