Correct wording, category for starter conversion (#235)

- Now a flowchart (and a renamed label)
- More explicit wording as per
https://github.com/hendricius/the-sourdough-framework/issues/234

book/baking/baking.tex

@@ -127,11 +127,12 @@ crust building. During the first stage of the bake, the dough
 increases in size. The water in your dough evaporates and pushes
 the whole dough upwards.
 
-\begin{figure}[!htb]
+\begin{flowchart}[!htb]
   \includegraphics[width=\textwidth]{baking-process-steam.jpg}
   \caption[Steam building with inverted tray]{How steam builds in your oven
-      using the later described inverted tray method.}
-\end{figure}
+      using the later described inverted tray method.}%
+      \label{flc:inverted-tray}
+\end{flowchart}
 
 Normally, under high heat a crust would form. Just like
 if you were to bake vegetables in your home oven, at some point