Add category-fse-is template

[bobbingwide]

Similar to the category display for FAQs it would be nice to be able to display the collection of quotes that are given in response to the question "What is FSE?".

Displaying ALL of the answers for a specific category is an interesting challenge.
It would be very easy to create a page to display the results using a custom query.
It's not so easy doing it for an archive display, since the number of posts to display is determined by WordPress core logic.
If I set the value to a high figure then I'll get more posts than I want on the "blog" page.