[Project] Introduce an "HTML recap" project to practice group coordination around git branches

**Which module(s) and week(s) does this change affect?**
Module(s): HTML/CSS but maybe actually done later on
Week(s): After HTML/CSS finishes

**What is the work that needs to be done?**

We want to motivate why git branches and git workflows are actually useful, and to get practice working with others.

Let's create a project where there are multiple pages, and a single consolidated CSS file.

We'll have groups edit different pages (and have to edit the shared CSS), and have them coordinate merging.

Maybe have people take turns on pages, so that only one person is editing a page at a time, but everyone edits at least two pages.

**Why is this work important to do?**

* Practice git workflows
* Articulate the value of git
* Work as a team
* Experience coordinating git workflows across teams