Support init a git repo and add generate file to git

[Zheaoli]

Feature Description

For now, pdm init command just add .gitignore file but not init the git repo locally

Problem and Solution

I propose support init git with following flag in pdm init command

1. --enable-git to represent init the git repo or not (maybe enable default?)
2. --default-branch to set the default branch name (main as default)

Additional Context

No response

Are you willing to contribute to the development of this feature?

• Yes, I am willing to contribute to the development of this feature.

[Zheaoli]

@frostming WDYT? I would like to submit a PR for this

[frostming]

It's good to add, also refer to related issue: #2220