tweak the learning objectives and tasks

I like the idea of a drop-in assignment to get students familiar with GitHub, but there currently aren't any tasks/measurable learning objectives.

In the intro,
> The goal of this course is to give you a brief introduction to GitHub. We’ll also provide you with materials for further learning and a few ideas to get you started on our platform.

brief introduction is vague. If you change the _next steps_ to tasks, then you can change the goals to specific and measurable learning outcomes.

The _optional_ next steps could be tweaked to build some measurable experience and profs/teachers could pick and choose which tasks to make mandatory:
|task| learn objective|
|---|---|
|open a PR| critique documentation or code|
|create a markdown file | compare markdown styles or create a document |
|create a repo| create and compare features in repo _maybe give a specific domain task_|

Then the intro would become:
> The goal of this course is to introduce code review and file creation in GitHub. You will use the resources here to critique documentation or code, compare styles, and create your own repository.