Design improvments for topic pages/category pages

[gbp]

On WDTK, we have increased the number of topic pages to a point where the index view is getting quite long and needs some better UI design.

Maybe we could collapse the long lists and have an option to expand to show everything. See current index view:

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On the individual topic page which uses the list view (where @category is set), it would also be good to improve UI.

This view is also used for the main search result list so we will need to be mindful of changes that work for both or separate the view.

Given the topic page is already filtered and showing a collection of results, my guess would be the search form won't be used as much as the main view. So maybe we could move the search form into the sidebar or hide it completely until it is revealed. See current list view:

Aside: If the "Follow" and "RSS" feed_link button styling could be fixed, that would be amazing.