Epic: collect needed documentation

### Overview

This issue tracks the documentation that needs to be added and the issue/pr where they would've been helpful in. The intention is to make it easy to note any missing documentation without having to create the issue at the same time.

### Action Items

- [x] [PR review guide](https://github.com/hackforla/peopledepot/issues/378#issuecomment-2335177512): #419
- [x] Django: [How to combine migrations](https://github.com/hackforla/peopledepot/issues/378#issuecomment-2339280759) #421
- [x] Git: [How to quickly checkout a PR](https://github.com/hackforla/peopledepot/issues/378#issuecomment-2369108593) #422
- [x] Git: [How to add a git alias](https://github.com/hackforla/peopledepot/issues/378#issuecomment-2369118008) #423
- [x] Django, Git: [How to resolve migration conflict](https://github.com/hackforla/peopledepot/issues/378#issuecomment-2378028404) #424
- [x] Git: [How to apply changes from one file to a different file](https://github.com/hackforla/peopledepot/issues/378#issuecomment-2380299270) #425
- [x] Git: [How to combine the last several commits into one](https://github.com/hackforla/peopledepot/issues/378#issuecomment-2461030505) #450
- [ ] Git: [How to update the docker compose command](https://github.com/hackforla/peopledepot/issues/378#issuecomment-2628262106)
- [x] Docker: [How to use new syntax replacing `docker-compose`](https://github.com/hackforla/peopledepot/issues/378#issuecomment-2628262106)
- [ ] Git: [Add troubleshooting section for GitHub SSH keys (for first time users or new machine)](https://github.com/hackforla/peopledepot/issues/378#issuecomment-2568603531)

### Resources/Instructions

#### How to use

1. Add a new comment for each documentation item needed using a copy of this template

```
### What's needed

- Description of what the missing documentation is about

### Draft (if written)

- Link to external docs with instructions (if applicable)

### Where it's useful

- Link to what prompted the need for this change/addition (if applicable)
- Situation where this could be used

### Where to put this

**contributing docs** should go in the `/docs/contributing/` folder or sub-folders:
- **how to guides** --> `/docs/contributing/howto/`
- **tutorials** --> `/docs/contributing/tutorial/`

### Audience

- Who or what role needs to perform this action

### Tags

- git, django, etc.
```

1. Add an action item here, linking to the comment below

1. Create an issue to add the documentation (can be done later by another person)

- Then, hide the original comment and add the new issue # to the action item

1. Work on the documentation issue and check off the action item (can be done later by yet another person)