Add exercise question for Split and combine arrays

Author: mlouhivu

numpy/split-combine/README.md

@@ -0,0 +1,8 @@
+## Split and combine arrays
+
+Continue with the previous 4x4 array
+
+1. Use `np.split()` function for splitting the array into two new 2x4 arrays.
+   Reconstruct the original 4x4 array by using `np.concatenate()`.
+2. Repeat the above exercise but create now 4x2 subarrays and then combine
+   them.