Update yogurt-cake.md w/ sugar

I forgot the sugar, both in this file and in the actual cake I made today. Because I thought the blogger mistakenly added sugar to the wet ingredient list, and I logically intended to add it to the dry. But when I followed the disparate instructions (which is why I write out my own recipes in a way that works for me), sugar of course wasn't listed there, so it didn't get added.

Author: aaronkelton

yogurt-cake.md

@@ -5,6 +5,7 @@ Mix wet:
 * 2 eggs
 * 1 container vegetable oil
 * 1 tsp vanilla extract
+* 2 containers sugar (add a reference link for why sugar is supposed to be added with wet)
 
 Mix dry:
 * 4 containers of flour