callTest
e.g. Prefer taking `pkgs.*` attrs directly as function arguments.
nixvimExtend
extend
This is our scope, so there's no need to be explicit. This also follows the precedent set by `lib.extend`, although that takes an overlay function.
This adds the `nixvimExtend` attribute to the generated standalone derivation, this attribute takes a module as an argument and returns a new standalone derivation with the initial module & the extended module merged together.
