Fix for viewport units, remove DataTable max-height (#2247)

* Add viewport units snapshot test

* Fix snapshot app

* Update snapshots

* Update DataTable max-height to 100%

* Update CHANGELOG.md

* Remove max height from DataTable CSS

tests/snapshot_tests/snapshot_apps/viewport_units.py

@@ -0,0 +1,14 @@
+from textual.app import App, ComposeResult
+from textual.widgets import Static
+
+
+class ViewportUnits(App):
+    CSS = """Static {width: 100vw; height: 100vh; border: solid cyan;} """
+
+    def compose(self) -> ComposeResult:
+        yield Static("Hello, world!")
+
+
+app = ViewportUnits()
+if __name__ == '__main__':
+    app.run()