[exps] Add data (and generation script) for arithmetic

examples/arithmetic/generate_dataset.py

+import numpy as np
+
+
+# Given a np array row, return a linear combination of the output
+def f(x: np.ndarray) -> np.ndarray:
+    return np.array((x[0] - x[1] - x[2]))
+
+
+if __name__ == "__main__":
+    arr1 = np.random.normal(size=(10000, 3))
+    arr2 = np.apply_along_axis(f, 1, arr1)
+    arr3 = np.random.normal(size=(10000, 3))
+    arr4 = np.apply_along_axis(f, 1, arr1)
+    np.save(file="data.npy", arr=arr1)
+    np.save(file="target.npy", arr=arr2)
+    np.save(file="test_data.npy", arr=arr3)
+    np.save(file="test_target.npy", arr=arr4)