docs: add extra parameter (#1649)

Author: JulienKode

docs/rtk-query/api/createApi.mdx

@@ -76,6 +76,7 @@ export const { useGetPokemonByNameQuery } = pokemonApi
   - `signal` - An [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal) object that may be used to abort DOM requests and/or read whether the request is aborted.
   - `dispatch` - The `store.dispatch` method for the corresponding Redux store
   - `getState` - A function that may be called to access the current store state
+  - `exta` - Provided as thunk.extraArgument to the configureStore getDefaultMiddleware option.
 - `extraOptions` - The value of the optional `extraOptions` property provided for a given endpoint
 
 #### baseQuery function signature