add incompleteness intro to sample textbook

Author: rzach

courses/sample/open-logic-sample.tex

@@ -148,6 +148,8 @@ \chapter{Natural Deduction}
 
 \part{Computability and Incompleteness}
 
+\olimport*[incompleteness/introduction]{introduction}
+
 % include intro to recursive function from computability part
 
 \olimport*[computability/recursive-functions]{recursive-functions}