Added a function to calculate GCD of Multiple numbers

[shreyventure]

Description of new feature, or changes

The function gcd_multiple_numbers, takes in variable number of arguments(numbers) and calculates the GCD for all those arguments.

Checklist

• [x] Your branch is up-to-date with the base branch
• [x] You've included at least one test if this is a new feature
• [x] All tests are passing