Add error code constants (#418)

* Add error code constants

* Woops forgot a space

structs.go

@@ -602,3 +602,55 @@ const (
 		PermissionManageServer |
 		PermissionAdministrator
 )
+
+const (
+	ErrCodeUnknownAccount     = 10001
+	ErrCodeUnknownApplication = 10002
+	ErrCodeUnknownChannel     = 10003
+	ErrCodeUnknownGuild       = 10004
+	ErrCodeUnknownIntegration = 10005
+	ErrCodeUnknownInvite      = 10006
+	ErrCodeUnknownMember      = 10007
+	ErrCodeUnknownMessage     = 10008
+	ErrCodeUnknownOverwrite   = 10009
+	ErrCodeUnknownProvider    = 10010
+	ErrCodeUnknownRole        = 10011
+	ErrCodeUnknownToken       = 10012
+	ErrCodeUnknownUser        = 10013
+	ErrCodeUnknownEmoji       = 10014
+
+	ErrCodeBotsCannotUseEndpoint  = 20001
+	ErrCodeOnlyBotsCanUseEndpoint = 20002
+
+	ErrCodeMaximumGuildsReached     = 30001
+	ErrCodeMaximumFriendsReached    = 30002
+	ErrCodeMaximumPinsReached       = 30003
+	ErrCodeMaximumGuildRolesReached = 30005
+	ErrCodeTooManyReactions         = 30010
+
+	ErrCodeUnauthorized = 40001
+
+	ErrCodeMissingAccess                             = 50001
+	ErrCodeInvalidAccountType                        = 50002
+	ErrCodeCannotExecuteActionOnDMChannel            = 50003
+	ErrCodeEmbedCisabled                             = 50004
+	ErrCodeCannotEditFromAnotherUser                 = 50005
+	ErrCodeCannotSendEmptyMessage                    = 50006
+	ErrCodeCannotSendMessagesToThisUser              = 50007
+	ErrCodeCannotSendMessagesInVoiceChannel          = 50008
+	ErrCodeChannelVerificationLevelTooHigh           = 50009
+	ErrCodeOAuth2ApplicationDoesNotHaveBot           = 50010
+	ErrCodeOAuth2ApplicationLimitReached             = 50011
+	ErrCodeInvalidOAuthState                         = 50012
+	ErrCodeMissingPermissions                        = 50013
+	ErrCodeInvalidAuthenticationToken                = 50014
+	ErrCodeNoteTooLong                               = 50015
+	ErrCodeTooFewOrTooManyMessagesToDelete           = 50016
+	ErrCodeCanOnlyPinMessageToOriginatingChannel     = 50019
+	ErrCodeCannotExecuteActionOnSystemMessage        = 50021
+	ErrCodeMessageProvidedTooOldForBulkDelete        = 50034
+	ErrCodeInvalidFormBody                           = 50035
+	ErrCodeInviteAcceptedToGuildApplicationsBotNotIn = 50036
+
+	ErrCodeReactionBlocked = 90001
+)