calculator.py

[xoxo444]

This PR enhances the existing calculator by adding three new functions:

1. modulus(a, b) – Returns the remainder of the division of a by b.
2. floor_divide(a, b) – Performs floor division, returning the largest integer less than or equal to a / b. Handles division by zero gracefully.
3. square_root(a) – Returns the square root of a. Handles negative numbers with an error message.

Additionally, sample print() statements have been added to demonstrate the usage of these functions.