Added Python solution for 53. Maximum Subarray (Tahanima#117)

* Added Python solution for 53. MaximumSubarray

* Changes added to Python solution for 53. MaximumSubarray

* Changes added to Python solution for 53. MaximumSubarray

Author: JoyKrishan

Algorithms/Medium/53_MaximumSubarray/Solution.py

@@ -0,0 +1,12 @@
+class Solution:
+    def maxSubArray(self, nums: List[int]) -> int:
+        current_sum, max_sub_sum = 0, nums[0]
+
+        for num in nums:
+            if current_sum < 0:
+                current_sum = 0
+                
+            current_sum += num 
+            max_sub_sum = max(current_sum, max_sub_sum)
+
+        return max_sub_sum