Make separate branches that can be used to create different template versions

`main` should include all of the files but `static` should delete the `.github` folder and `dynamic` should delete the `course_instructions.md` file. In addition, `main` should have an instructors guide somewhere (see #6) and that file should not appear in either the `static-course` nor the `dynamic-course` branches.

Follow-up: Before doing this, check that using either branches from the template will create a `main` branch in the resulting repo. If not, maybe come up with an alternative.