Add syntax comment to \marginfig.

MarginNotes.sty

@@ -38,6 +38,19 @@
 	\RequirePackage{ifthen}
 
 	\newcommand{\marginfig}[5][0pt]{%
+		% Syntax:
+		% \marginfig[
+		%	vertical_offset
+		% ]{
+		%	graphic_file_name
+		% }{
+		%	(width|height)=lengthvalue
+		% }{
+		%	label
+		% }{
+		%	caption
+		% }
+		%
 		% This strut ensures that the margin figure is counted as part of the 
 		% following paragraph and is vertically aligned with it.
 		\strut%