Create a Guide/Template: How to resolve PR merge conflicts when another contributor made a previous PR

### Dependency
- hackforla/peopledepot#166

### Overview

We need documentation to guide developers in resolving this common problem. 2 devs start with the same base commit, the first one to create a PR is okay, but the 2nd dev to create a PR will have some conflicts in their PR, even though it runs fine.

### Action Items

- [ ] write doc to explain and guide to find the solution
- [ ] check the website team's guide on the same topic
- [ ] if there are common sections
- [ ] copy the relevant portion into a new guide in the Engineering CoP docs repo. Note which projects are referencing the guide.
- [ ] link from our docs while removing those sections
- [ ] notify website team to examine the content and link it from their docs

### Resources/Instructions
- Google Drive Folder for this Guide's documents and shortcuts (to documents in other locations) [0120 [DRAFT] How to resolve PR merge conflicts when another contributor made a previous PR](https://drive.google.com/drive/folders/1W0utd7DIXKHSXXS9llekS2ZmqZXQOp0j)
- website team's page on [how to resolve merge conflicts](https://github.com/hackforla/website-wiki/blob/main/docs/How-to-Resolve-Merge-Conflicts.md)

## Discussion

The preferred solution is to rebase the new PR to the new HEAD of the main branch and resolve any conflicts so that the PR can be merged smoothly.

See [discussion](https://github.com/hackforla/peopledepot/discussions/169) on this topic