feat(git): Create Git Repository

[refcell]

Description

Adds a --git flag to amble that allows amble to automatically create a github repo under the user's username.

The --git flag should be of type Option<Option<String>> where the inner string is the user's github username. If it is not specified, amble should try to grab the username like done for the cargo toml repository url field.

When the --full flag is provided, git repo generation should be enabled by default.

[quangkeu95]

As I understand that if the --git flag is set, then we init the git repository first, then we set the remote tracked repository to the url that includes the github user's username, is it right?

[quangkeu95]

Still not knowing how to grab the username if user input is not provided, please enlighten me !! Also, for the user remote origin url, should I use this format by default: git@github.com:username/new_repo ?