add empty line to end of file

Fixes #418

learners/misconceptions-mcqs.md

@@ -200,4 +200,4 @@ However, when supported by the appropriate scaffolding of information and contex
 Just like the other exercise types explored in the main curriculum, designing effective multiple choice questions can be difficult but it is worth persevering with: a good set of exercises is a great asset to a lesson and especially helpful to instructors teaching it.
 
 [^1]: See chapter 1, _How Does Students' Prior Knowledge Affect Their Learning?_,
-      of [Ambrose et al. 2010](learners/reference.md#litref).
+      of [Ambrose et al. 2010](learners/reference.md#litref).