Add styling of 'x' and 'y' denoting axes

Using match would have been an alternative, but \lstinline was chosen for symmetry with the styling of 'curves'.

chapters/annotations.tex

@@ -99,9 +99,7 @@ \subsection{Annotations for Figures}\label{annotations-for-figures}
 end Plot;
 \end{lstlisting}
 
-A \lstinline!Plot! can contain several \lstinline!curves!, see
-\cref{plot-curves}, that all share a common x and y axis with properties
-described in \cref{axis-properties}.
+A \lstinline!Plot! can contain several \lstinline!curves!, see \cref{plot-curves}, that all share a common \lstinline!x! and \lstinline!y! axis with properties described in \cref{axis-properties}.
 
 Both \lstinline!Figure! and \lstinline!Plot! can have an optional title. When
 the \lstinline!Figure! \lstinline!title! is the empty string (the default), the