fuseadf man: add info about unmounting.

Author: t-w

doc/fuseadf.1

@@ -10,6 +10,8 @@ a volume of an ADF (an image of a floppy or a hard disk in Amiga format)
 and to access the data the volume contains, either in read-write (default)
 or in read-only mode (set with \fB-o ro\fR).
 .PP
+Mounted filesystem can be unmounted with the \fBumount\fR command.
+.PP
 What is important - mounting using FUSE can be done by a regular user
 (no need for root-level access).
 .PP