add cl-diskspace package to ritherdon-archive.asd.

This package grabs disk information from the OS -- and can display it in human
readable form. Looking to create a 'Disk Info.' section on the dashboard page to
help users decide when they need to start deleting snapshot data or move to a
machine with a bigger disk.

At the time of this commit, no features have been implemented yet.

ritherdon-archive.asd

@@ -41,6 +41,7 @@
 	       #:cl-slug        ; Asciify and slugify strings
 	       #:str            ; String manipulation (easier than built-in)
                #:copy-directory ; Copy Directories using Native cp
+               #:cl-diskspace   ; Get Disk Info.
 	       )
   :pathname "src/"
   ;; :serial t