#699 Update newsroom block to allow filtering by author category

[thetwopct]

LMK if this does what you want 👍

https://pr-708-cncfci.pantheonsite.io/

[cjyabraham]

I've set it up on this page. On the back-end, it looks like this, correctly showing the last 3 posts with the End User author cat:

On the front-end, however, it just appears to show the last 3 blog posts without filtering by author cat:

[cjyabraham]

Looking good. Thanks.