feat: add is premium user status

Author: temamagic

types.go

@@ -183,6 +183,10 @@ type User struct {
 	//
 	// optional
 	IsBot bool `json:"is_bot,omitempty"`
+	// IsPremium true, if user has Telegram Premium
+	//
+	// optional
+	IsPremium bool `json:"is_premium,omitempty"`
 	// FirstName user's or bot's first name
 	FirstName string `json:"first_name"`
 	// LastName user's or bot's last name