`SMSG_VENDOR_INVENTORY` undefined for 3.4.1/3.4.2 builds.

[heyitsbench]

I did try to manually define the opcode for 3.4.1 (0x25B9 iirc) using the 3.4.0 module, but the structure was also incorrect, and I don't know enough at this time to be able to fix it myself unfortunately.

[ratkosrb]

You can find a full opcodes enum for 3.4.1 here:
https://github.com/ratkosrb/WowPacketParser/blob/classic/WowPacketParser/Enums/Version/V3_4_1_47014/Opcodes.cs

[heyitsbench]

You can find a full opcodes enum for 3.4.1 here: [WPP fork]

Does seem that fork also has an issue with the structure of the packet, at least with 3.4.1 47720.