add entry for queryCacheKey in createApi docs

Author: HaakonSvane

docs/rtk-query/api/createApi.mdx

@@ -91,6 +91,7 @@ export const { useGetPokemonByNameQuery } = pokemonApi
   - `endpoint` - The name of the endpoint.
   - `type` - Type of request (`query` or `mutation`).
   - `forced` - Indicates if a query has been forced.
+  - `queryCacheKey`- The computed query cache key
 - `extraOptions` - The value of the optional `extraOptions` property provided for a given endpoint
 
 #### baseQuery function signature