Created harshad_numbers.py (#9023)

* Created harshad_numbers.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update harshad_numbers.py

Fixed a few errors

* Update harshad_numbers.py

Added function type hints

* Update harshad_numbers.py

Fixed depreciated Tuple and List usage

* Update harshad_numbers.py

Fixed incompatible types in assignments

* Update harshad_numbers.py

Fixed incompatible type assignments

* Update maths/harshad_numbers.py

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* Update maths/harshad_numbers.py

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* Raised Value Error for negative inputs

* Update maths/harshad_numbers.py

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* Update maths/harshad_numbers.py

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* Update maths/harshad_numbers.py

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

* Update harshad_numbers.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update harshad_numbers.py

* Update harshad_numbers.py

* Update harshad_numbers.py

* Update harshad_numbers.py

Added doc test to int_to_base, fixed nested loop, other minor changes

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>