Main branch must be 'main' not 'master'

[kapilbhosale]

When we clone the repo, it comes with a master branch. As per the new git standards, it must be main. One can make changes after cloning it, I believe its good to have 'main' in the cloned repo itself.

Reference: The default branch name in Git was changed from "master" to "main" in order to promote a more inclusive language.