Provides current stack bonuses for an item in the tooltip

First thing you'll need is the BepInExPack. If you don't have it, get it here and follow the installation instructions.
Afterwards, get the zip file from releases and extract the ItemStats folder in BepInEx/plugins. That's it!
In order to use API, add a Bepin SoftDependency to your BaseUnityPlugin annotations. Make sure to check if ItemStats is loaded before trying to use it
Then, create an ItemStatDef for your item (see ItemStatDefinitions.cs for examples).
Use the R2API ItemApi Submodule to add your item and get its ItemIndex.
After that, simply call ItemStatsMod.AddCustomItemStatDef(myItemIndex, myItemStatDef)
To create an item stat modifier, extend from AbstractStatModifier. Check ItemStats.StatModification.Modifiers for examples
Add an instance of the class with ItemStatsMod.AddStatModifier(new MyStatModifier())
You will first need the following libraries:
Open the solution, link the libraries in the Lib folder, DL the required NuGet package and compile.