fix(docs): add missing param in mocked create (Vitest guide) (#2166)

docs/guides/testing.md

@@ -176,7 +176,7 @@ const createUncurried = <T>(stateCreator: zustand.StateCreator<T>) => {
 }
 
 // when creating a store, we get its initial state, create a reset function and add it in the set
-export const create = (<T>() => {
+export const create = (<T>(stateCreator: zustand.StateCreator<T>) => {
   console.log('zustand create mock')
 
   // to support curried version of create