Add exponential Search solution in C++

[MUKUL-RAJPUT2004]

Overview

Adds Exponential Search implementation to find an element in a sorted array using bounding and binary search.

Changes

• New file: c++/Binay Search/exponential_search.cpp with binarySearch helper and exponentialSearch function.
• Test case [2,3,4,10,40,50,60,70,80] for target=40 (output: index 3).
• Comments on logic and O(log n) time.

Testing

• Tested locally; output: Element found at index: 3

Context

Hacktoberfest 2025 contribution.

Checklist:

• Code style consistent.
• Includes example and comments.
• No dependencies added.

Contributor: Mukul Rajput (@MUKUL-RAJPUT2004) | Date: October 11, 2025