Implement simple stack class in stack.py

**Title:** Add Stack Implementation in data_structures

**Description:**
This PR adds a simple Stack data structure implementation in Python to the `data_structures` directory. The class supports `push`, `pop`, and `is_empty` methods, with error handling for popping from an empty stack.

Let me know if you would like me to add tests or further documentation.

Author: Bylerma

stack.py

@@ -0,0 +1,15 @@
+# Example: Simple Stack implementation
+class Stack:
+    def __init__(self):
+        self.items = []
+
+    def push(self, item):
+        self.items.append(item)
+
+    def pop(self):
+        if not self.is_empty():
+            return self.items.pop()
+        raise IndexError("pop from empty stack")
+
+    def is_empty(self):
+        return len(self.items) == 0