Center TikZ figures

Because it looks better

book/bread-types/bread-types.tex

@@ -163,10 +163,12 @@ few steps, you can stop buying bread forever. This works with
 any flour, including gluten-free options.
 
 \begin{figure}[!htb]
+\begin{center}
   \input{figures/fig-process-flat-bread.tex}
   \caption{The process of making a flatbread is very simple, requiring very little effort. This
   type of bread is especially handy for busy bakers.}%
   \label{fig:flat-bread-process}
+\end{center}
 \end{figure}
 
 This is my go-to recipe that I~use to make bread whenever