missed keybinding in cwm.1

[Mikhail]

Missed keybinding in the man page:

diff --git a/app/cwm/cwm.1 b/app/cwm/cwm.1
index 3b4e76e83..3f8f5d241 100644
--- a/app/cwm/cwm.1
+++ b/app/cwm/cwm.1
@@ -103,6 +103,8 @@ Reverse cycle through currently visible windows.
 Delete current window.
 .It Ic CM-[n]
 Toggle visibility of group n, where n is 1-9.
+.It Ic CM-0
+Toggle visibility of all groups.
 .It Ic CM-a
 Toggle visibility of all groups.
 .It Ic CM-g