Add git lessons fixture file
user
```ruby
def git_lessons
  {
    'A Deeper Look at Git' => {
      title: 'A Deeper Look at Git',
      description: 'Beyond just `$ git add` and `$ git commit`...',
      is_project: false,
      url: '/git/lesson_a_deeper_look_at_git.md',
      identifier_uuid: '52b17564-0e1d-4c4f-adfa-acba53bf9126',
    },
    'Using Git in the Real World' => {
      title: 'Using Git in the Real World',
      description: "We've just scratched the surface, so here's what to be aware of as you start developing more and more using Git.",
      is_project: false,
      url: '/git/lesson_using_git_in_the_real_world.md',
      identifier_uuid: 'c8b7ccc1-8a16-4545-9d46-b9091d45c6b4',
    },
  }
end
```
assistant