Contributing.md: Add docker rebuilds info

[ExperimentsInHonesty]

Dependency

• Update Docker Compose Dev With New Features #1443

Overview

We need to add some text to the contributing about slowness with docker to help those that experience it.

Action Items

• Define what needs to be in this section
  • Jason is going to add info about a smaller version of Git
  • Link and description of who should take on this issue in icebox about docker rebuilds Update Docker Compose Dev With New Features #1443

Resources/Instructions

https://github.com/hackforla/website/blob/gh-pages/CONTRIBUTING.md