Mentioning dmenu.gif in the README §Files section

README

@@ -18,6 +18,7 @@ The files are:
 • ./Makefile:   The makefile.
 • ./config.h:   The hardcoded default configuration for XMenu.
 • ./config.mk:  The setup for the makefile.
+• ./demo.gif:   A gif demonstrating how XMenu works.
 • ./xmenu.1:    The manual file (man page) for XMenu.
 • ./xmenu.c:    The source code of XMenu.
 • ./xmenu.sh:   A sample script illustrating how to use XMenu.