Add a short description of INDI (Instrument Neutral Distributed Interface)

doc/man1/rotctl.1

@@ -828,7 +828,15 @@ for INDI using the local domain on Linux:
 .RB $ " rotctl -m 2001 -r @/tmp/indiserver"
 .EE
 .in
-.
+.PP
+INDI (Instrument Neutral Distributed Interface) is an LGPLv2
+software to control astronomical equipment,
+including telescope mounts that can be used to rotate antennas.
+.PP
+For more information see
+.UR https://indilib.org/
+indilib.org
+.UE
 .
 .SH BUGS
 .