API used by Vortex extensions.
Technically you don't need this module. When your extension run (regularly), vortex will inject the vortex-api module, so this module is mainly relevant as a reference and to provide command completion in an IDE.
The API reference is available at https://nexus-mods.github.io/vortex-api. However, for technical reasons this reference may currently contain classes and interfaces that are not actually exposed through the api.