Is your feature request related to a problem? Please describe.
The trigger for Item type equipped does not include offhand but every other sort of weapon

Describe the solution you'd like
That it would be added

Describe alternatives you've considered
Can make it custom ofc but seeing as every other type is included I believe offhand should be aswell

Additional context

There is no special off hand weapon type. One handed swords, axes, daggers, fist weapons can be equipped in either slot.

This is not true for the Classic era. There are plenty of items that can only be equipped in either the Main Hand or the Off Hand exclusively.

Main Hand example:
https://tbc.wowhead.com/item=34336/sunflare
Off Hand example:
https://tbc.wowhead.com/item=34949/swift-blade-of-uncertainty

Note that these are simply the first I found, the MH/OH status are not unique to simply those two weapons or even daggers.

Alternatively the user may be referring to an actual off hand item such as:
https://tbc.wowhead.com/item=34179/heart-of-the-pit

Which do exist in retail, ex: https://www.wowhead.com/item=189860/forbidden-truth