mwan3: Update documentation information for mwan3.user file

Signed-off-by: James White <james@jmwhite.co.uk>

net/mwan3/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=mwan3
 PKG_VERSION:=2.10.3
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 PKG_MAINTAINER:=Florian Eckert <fe@dev.tdt.de>
 PKG_LICENSE:=GPL-2.0
 PKG_CONFIG_DEPENDS:=CONFIG_IPV6

net/mwan3/files/etc/mwan3.user

@@ -8,9 +8,13 @@
 # There are three main environment variables that are passed to this script.
 #
 # $ACTION
-#      <ifup>         Is called by netifd and mwan3track
-#      <ifdown>       Is called by netifd and mwan3track
-#      <connected>    Is only called by mwan3track if tracking was successful
-#      <disconnected> Is only called by mwan3track if tracking has failed
-# $INTERFACE	Name of the interface which went up or down (e.g. "wan" or "wwan")
-# $DEVICE	Physical device name which interface went up or down (e.g. "eth0" or "wwan0")
+#      <ifup>         Is called by netifd and mwan3track.
+#      <ifdown>       Is called by netifd and mwan3track.
+#      <connected>    Is only called by mwan3track if tracking was successful.
+#      <disconnected> Is only called by mwan3track if tracking has failed.
+# $INTERFACE	Name of the interface an action relates to (e.g. "wan" or "wwan").
+# $DEVICE	Physical device name of the interface the action relates to (e.g. "eth0" or "wwan0").
+#               Note: On an ifdown event, $DEVICE is not available, use $INTERFACE instead.
+#
+# Further documentation can be found here:
+# https://openwrt.org/docs/guide-user/network/wan/multiwan/mwan3#alertsnotifications