Create merge-arrays.py

efficient solution, additionally the arrays can be added together and then sorted via .sort for the same effect, this is much slower however.

merge-arrays.py

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+class Solution:
+    def merge(self, nums1: List[int], m: int, nums2: List[int], n: int) -> None:
+        """
+        Do not return anything, modify nums1 in-place instead.
+        """
+        p1 = m - 1
+        p2 = n - 1
+        p_main = m + n - 1  # Pointer to array location of next addition
+        # Pointers start from the back to avoid shifting the array along
+        while p2 >= 0:  # Iterate until p2 is negative, this means both p1 and p2 are exhausted
+            if p1 >= 0 and nums1[p1] > nums2[p2]:
+                nums1[p_main] = nums1[p1]
+                p1 -= 1
+            else:
+                nums1[p_main] = nums2[p2]
+                p2 -= 1
+            p_main -= 1