Add a way to quote for command arguments and use for key in list-keys,

GitHub issue 5153.

tmux.1

@@ -6286,12 +6286,17 @@ of the variable respectively.
 .Ql q:\&
 will escape
 .Xr sh 1
-special characters or with a
+special characters; with a
 .Ql h
 suffix, escape hash characters (so
 .Ql #
 becomes
-.Ql ## ) .
+.Ql ## ) ;
+or with
+.Ql a
+escape
+.Nm
+command arguments.
 .Ql E:\&
 will expand the format twice, for example
 .Ql #{E:status\-left}