Add new exponent operation to calculator

[ghost]

Description

This PR adds a new operation for computing the exponent to the calculator program. The exponent operation raises a base number to the power of an exponent.

Summary of Changes

• Added a new function named exponent to the calculator.py file. This function takes two arguments, base and exponent, and returns the result of base raised to the power of exponent.
• Modified the calculator function to include a new option for the exponent operation in the user menu.
• Implemented the handling of the exponent operation in the calculator function. When the user selects the exponent operation, the exponent function is called with the user-provided numbers, and the result is printed in the same format as the other operations.

Please review and merge this PR. Thank you!

Fixes #1.

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[kevinlu1248]

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[kevinlu1248]

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