Create a new page for create a project with Git

What does this MR do and why?

In this MR, a new page is added to the Use Git --> Basic operations section. The information on this page is Git-related info from the Create a project page. It is part of a larger issue to reorganize Git documentation to improve the user experience by separating GitLab UI and Git CLI tasks.

Navigation

- Basic operations
  - Create a project
  - Clone a repository
  - Create a branch
  - Stage, commit, and push changes
  - Stash changes
  - Add files to your branch
  - Merge your branch

Related issues

• Issue: #499459
• Child item: #499466 (closed)
• MR to update navigation: Add create project with Git push nav item (gitlab-docs!5160 - merged)