[#286] reputation: Refactor and document package functionality

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

reputation/doc.go

@@ -0,0 +1,34 @@
+/*
+Package reputation collects functionality related to the NeoFS reputation system.
+
+The functionality is based on the system described in the NeoFS specification.
+
+Trust type represents simple instances of trust values. PeerToPeerTrust extends
+Trust to support the direction of trust, i.e. from whom to whom. GlobalTrust
+is designed as a global measure of trust in a network member. See the docs
+for each type for details.
+
+Instances can be also used to process NeoFS API V2 protocol messages
+(see neo.fs.v2.reputation package in https://github.com/nspcc-dev/neofs-api).
+
+On client side:
+	import "github.com/nspcc-dev/neofs-api-go/v2/reputation"
+
+	var msg reputation.GlobalTrust
+	trust.WriteToV2(&msg)
+
+	// send trust
+
+On server side:
+	// recv msg
+
+	var trust reputation.GlobalTrust
+	trust.ReadFromV2(msg)
+
+	// process trust
+
+Using package types in an application is recommended to potentially work with
+different protocol versions with which these types are compatible.
+
+*/
+package reputation