Add a flowchart environnement and its listof

So we can more easily access those flowcharts from pdf and website,
rather than looking in the crowded list of figures.

book/non-wheat-sourdough/non-wheat-sourdough.tex

@@ -28,7 +28,7 @@ period, the bread can be baked. Due to the lack
 of gluten development, the final bread will feature a denser
 crumb compared to wheat.
 
-\begin{figure}[!htb]
+\begin{flowchart}[!htb]
 \begin{center}
   \input{figures/fig-non-wheat-process.tex}
   \caption[Process for non-wheat sourdough bread]{A visualization of the
@@ -37,7 +37,7 @@ crumb compared to wheat.
       ingredients are simply mixed together.}%
   \label{fig:non-wheat-sourdough}
 \end{center}
-\end{figure}
+\end{flowchart}
 
 This chapter will focus on making rye bread. The flour could
 be replaced with einkorn or emmer based on your preference.