Hook into WildStacker

[Poslovitch]

Description

Is your feature request related to a problem?

Requested on Discord.

Describe the solution you'd like us to implement.

Add a hook and API for it so that addons (such as Levels) can gather data.

Describe alternatives you've considered.

As there are a few of these "stackers" plugins around, it may be interesting to provide an "interface"-based API so that we can easily add support for all of them.
Or maybe even a similar thing so that addons that would add those "Stacking" behaviours could be also supported.

Additional context

I hoped we'd have had more time before needing to implement hooks for premium plugins, but sadly, we have to do it at some point if we want to remain competitive.