Adding upstream version 0.12.0.

Signed-off-by: Daniel Baumann <daniel@debian.org>

tests/snapshot_tests/snapshot_apps/empty_add_col.py

@@ -0,0 +1,17 @@
+from textual.app import App, ComposeResult
+from textual_fastdatatable import DataTable
+
+
+class TableApp(App):
+    def compose(self) -> ComposeResult:
+        yield DataTable()
+
+    def on_mount(self) -> None:
+        table = self.query_one(DataTable)
+        table.add_column("Foo")
+        table.add_rows([("1",), ("2",)])
+
+
+app = TableApp()
+if __name__ == "__main__":
+    app.run()