Rename visible property to display, add setter

tests/test_dom.py

@@ -0,0 +1,25 @@
+import pytest
+
+from textual.css.errors import StyleValueError
+from textual.dom import DOMNode
+
+
+def test_display_default():
+    node = DOMNode()
+    assert node.display is True
+
+
+@pytest.mark.parametrize(
+    "setter_value,style_value",
+    [[True, "block"], [False, "none"], ["block", "block"], ["none", "none"]],
+)
+def test_display_set_bool(setter_value, style_value):
+    node = DOMNode()
+    node.display = setter_value
+    assert node.styles.display == style_value
+
+
+def test_display_set_invalid_value():
+    node = DOMNode()
+    with pytest.raises(StyleValueError):
+        node.display = "blah"