All directives and pipes must now be tagged with one ore more
public NgModule, from which they are exported.
If an item is exported transitively via a re-exported internal NgModule
then it may be that the item appears to be exported from more than
one public NgModule. For example, there are shared directives that
are exported in this way from `FormsModule` and `ReactiveFormsModule`.
The doc-gen will error and fail if a directive or pipe is not tagged correctly.
NgModule pages now list all the directives and pipes that are exported from it.
Directive and Pipe pages now list any NgModule from which they are exported.
Packages also now list any NgModules that are contained - previously they were
missed.
PR Close#25734
Pete Bacon Darwin