scripts: unified and renamed wallpaper script(s)

.config/sxiv/exec/key-handler

@@ -2,7 +2,8 @@
 while read file
 do
         case "$1" in
-        "w") wallpaper "$file" & ;;
+        "w") wallpaper desktop "$file" & ;;
+        "l") wallpaper lock "$file" & ;;
         "c")
 		[ -z "$destdir" ] && destdir="$(sed "s/\s.*#.*$//;/^\s*$/d" ~/.config/bmdirs | awk '{print $2}' | dmenu -l 20 -i -p "Copy file(s) to where?" | sed "s|~|$HOME|g")"
 		[ -z "$destdir" ] && exit