Add function to calculate area of triangle using Heron's formula (#4065)

* Update area.py

Modified area of triangle function. Added a new algorithm to calculate area when 3 sides are known

* Add files via upload

* Update area.py

* Update area.py

* Update area.py

* Update area.py

* Remove unnecessary whitespace

Co-authored-by: Dhruv Manilawala <dhruvmanila@gmail.com>