Add trigger support for softinteract

[gjfLeo]

There's "Soft Enemy" and "Soft Friend" in unit info triggers. Can we support "softinteract" as well? It'll be useful when tracking cooldowns /items count related with GameObject, such as Overload Sporefused Herb.

Considering that the "softinteract" unit may be not a creature, maybe more works required?

[emptyrivers]

hmm, i wasn't convinced when i added softfriend/softenemy, and im still not convinced today. Like, I get the use case, i even made something similar myself, but I just don't see how select(6,UnitGUID("softinteract")) == "1337h4x0rz" is so broadly useful and/or annoying to implement in custom code to warrant supporting in the builtins.

Also as you mention, softinteract is usually going to be one GameObject or another, and most of the unit info triggers aren't able to glean interesting information about an object. That IMO kills the simple implementation ("just add Soft Interact to the Unit dropdown") on the grounds of "try to not accidentally lie to your users about what WeakAuras can do".

Did you have a use case in mind beyond just "is my soft interact target an herb i can overload"?