Center TikZ figures

Because it looks better

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

@@ -27,11 +27,13 @@ of gluten development, the final bread will feature a denser
 crumb compared to wheat.
 
 \begin{figure}[!htb]
+\begin{center}
   \input{figures/fig-non-wheat-process.tex}
   \caption{A visualization of the process to make non-wheat sourdough bread.
   The process is much simpler than making wheat sourdough bread. There is
   no gluten development. The ingredients are simply mixed together.}%
   \label{fig:non-wheat-sourdough}
+\end{center}
 \end{figure}
 
 This chapter will focus on making rye bread. The flour could