Fix compiler error "does not satisfy the constraint 'ObjectNested'"

[colinrotherham]

This PR fixes #5606

Affects ConfigurableComponent<CustomConfig> in v5.8.0 where CustomConfig doesn't extend ObjectNested

   * @virtual
-  * @template {ObjectNested} [ConfigurationType={}]
+  * @template {Partial<Record<keyof ConfigurationType, unknown>>} [ConfigurationType=ObjectNested]
   * @template {Element & { dataset: DOMStringMap }} [RootElementType=HTMLElement]
   * @augments GOVUKFrontendComponent<RootElementType>

I've shared the config type via Schema Schema<ConfigurationType> for use in @param and @returns too

This may not have affected JSDoc due to The Empty Object Type in TypeScript