✅ Add test for marimo dataset

Author: srivarra

tests/datasets/test_basic.py

@@ -0,0 +1,7 @@
+from annsel.datasets import marimo_dataset
+
+
+def test_marimo_dataset():
+    adata = marimo_dataset()
+    assert adata.n_obs == 100
+    assert adata.n_vars == 100