feat: added binomial heap data structure

[sarveshjoshi29]

Description of Change

This PR adds a C++ implementation of the Binomial Heap (min-heap) data structure under the data_structures folder.
A binomial heap is a collection of binomial trees that supports the following operations : insertion, get-min, pop-min, and merging two binomial heaps in $O(\log n)$ time.
The implementation contains:

• Full documentation obeying the Doxygen guidelines.
• Self-test cases covering all operations and various edge cases (insertion order, duplicate values, popping, merging, and unifying heaps) with assertions.

Checklist

• Added description of change
• Added file name matches File name guidelines
• Added tests and example, test must pass
• Added documentation so that the program is self-explanatory and educational - Doxygen guidelines
• Relevant documentation/comments is changed or added
• PR title follows semantic commit guidelines
• Search previous suggestions before making a new one, as yours may be a duplicate.
• I acknowledge that all my contributions will be made under the project's license.

Notes: Adds a complete, self-tested, and documented implementation of the Binomial Heap to data_structures. This is also my first ever PR, I apologize if I have missed out anything, thanks