Overall tracking issue for advanced content

This issue provides an overview of the content that needs to be added to the training manual for some of our more advanced audiences. There is some duplication between this issue and an existing project on GitHub from our amazing Programs team 🎉 .

| Topic | Issue (If any) | PR | Done |
|-------------------------------------------------------- |----------------- |------ |------ |
| Add GitHub Package Management | #227 | | |
| Add Insights | #226 | | |
| Add Codespaces | #226 | | |
| Add Actions | #224 | #237 | ✅ |
| Personal Access Tokens (PATs) | | #241 | ✅ |
| Configure GPG Keys | | #253 | |
| Branching strategies for multi-environment deployments | | | |
| Branch protection to match the above | | | |
| Introduction to the GitHub API and examples of usage | | | |
| Introduction to GraphQL and examples of usage | | | |
| Overview of CI/CD & where GitHub fits in | | | |
| Repository best practices | | [Similar PR for admin](https://github.com/githubtraining/admin-training/pull/67)
[Similar content here](https://github.github.com/services-workflow-guide/#/branch-protection) | |
| Create `.gitignore` files and usage | |#243 | ✅ |
| Git LFS (existing content from @beardofedu) | | #255 | |
| Submodules | #78 | #256 | |
| Subtrees | | #256 | |
| Git Sparse checkout | | | |
| git-filter-branch / git-filter-repo | | | |
| Git internals deep dive | | | |
| git stash | | | |
| GitHub Packages | | | |

If you are available to tackle any of these tasks, just assign yourself to the issue, if an issue doesn't exist just throw your name next to it, but I expect to create the needed issues before tomorrow the 11th.