Add my configs/customizations, point to upstream repo in README.md

config.def.h

@@ -1,5 +1,11 @@
 /* See LICENSE file for copyright and license details. */
 
+/* NOTE: config.h replaces this file, but I'm keeping this one to help distinguish
+ * between others' patches (published via suckless.org) and my own additions.
+ *  - to see others' patches, diff config.def.h against upstream's config.def.h
+ *  - to see my additional changes, diff config.h against config.def.h
+ */
+
 /* appearance */
 static unsigned int borderpx  = 1;        /* border pixel of windows */
 static unsigned int snap      = 32;       /* snap pixel */