Install community.library_inventory_filtering_v1 for PR docs builds.

This is required to make CI in #698 pass.

.github/workflows/docs-pr.yml

@@ -32,6 +32,7 @@ jobs:
       init-extra-html-theme-options: |
         documentation_home_url=https://${{ github.repository_owner }}.github.io/${{ github.event.repository.name }}/branch/main/
       render-file-line: '> * `$<status>` [$<path_tail>](https://${{ github.repository_owner }}.github.io/${{ github.event.repository.name }}/pr/${{ github.event.number }}/$<path_tail>)'
+      extra-collections: community.library_inventory_filtering_v1
 
   publish-docs-gh-pages:
     # for now we won't run this on forks