Needs definition for sourdough starter

[sstevens2]

Need to add a glossary for this lesson.

The new file should go in the learners/, click the "Add file" button in the top upper right-hand side of the screen to add a new file called reference.md

In the reference.md file add the following section to the file

---

title: Reference

## Glossary

sourdough starter : A fermented culture of wild yeast, often made by combining flour and water and > allowing time for fermentation or through propagation.

[emcaulay]

I will start work on this issue.