Changed default branch to main for new projects

[RCC-CCN]

Changed the default branch of the initialized repository from "master" to "main" to adhere to github default behavior.

[friendlyanon]

Sorry, not interested in this nonsense peddled by Microsoft. This is also covered by the non-goals of the project.

For personal use, it's trivial to create a .pyz from the project with such changes.

[RCC-CCN]

While I understand this change might not be wanted or needed and that changing the behaviour is trivial, in the non-goals (at least as I understood it) is specified that file generation for Github given it's popularity is part of the goals.
Github has for some time used main as default name for it's starting branch and this change might have reflected that.

If the section of the non-goals is limited to .github files then it's understandable.

[friendlyanon]

The generated projects' connection to GitHub is limited to the .github directory, because that's where CI files go on GitHub and CI is an essential part of projects. Even if they go unused, because the user wishes to use a different vendor, they are easy to remove and show how to setup CI for a CMake managed project.

The readme also highlights that "cmake-init is an opinionated CMake project initializer" and I don't agree with Microsoft.