refactor(cli): use jinja over copier

[rnbguy]

Closes #166

• removes git and copier dependency
• includes templates in atomkraft package
• atomkraft init works offline now
• atomkraft init uses correct templates on PR workflows

Otherwise, atomkraft init stays virtually the same.

Since this removes git dependency, init doesn't initialize a git repo anymore.

• added cli test

[rnbguy]

CI will be successful with the newer Modelator version.

[ivan-gavran]

Approve. I only have one doubt: is having .gitkeep files a feature or a bug for the users? On the one hand, if a github repo is not initialized, does it make sense to add those "junk" files? On the other hand, it is likely they will initialize a repo themselves.

[rnbguy]

.gitkeep is a hack to include empty directories into git repo 😅

we probably have to rethink how we initialize a project directory. Maybe we keep a map of empty directories and create them on the fly.