SPATZ migration + proper directory structure

spatz/transforms/transform.py

@@ -0,0 +1,12 @@
+import numpy as np
+
+from numpy.typing import ArrayLike
+from typing import Any, Tuple
+
+
+class Transform:
+    def apply(self, t: float, x: np.array):
+        y = self(t, x)
+        assert x.shape == y.shape, "Transform has to maintain the array's shape."
+
+        return y