Add crumb structures overview to debugging

This adds a full overview of different crumb structures to the debugging
section.

book/troubleshooting/crumb-structures/crumb-structures.tex

@@ -3,6 +3,12 @@ your fermentation process has gone. You can also spot common flaws
 of improper technique. This chapter will provide you with information
 that you can use to debug your baking process.
 
+\begin{figure}
+  \includegraphics[width=\textwidth]{crumb-structures-overview}
+  \caption{An overview of different crumb structures}
+  \label{fig:crumb-structures-overview}
+\end{figure}
+
 \subsection{Perfect fermentation}
 
 \begin{figure}