Improved empty catalog states

We realised that empty catalog pages didn’t do a great job of helping you to understand how to use the application. When you sign in for the first time, you see an empty catalog table, but no guidance on how to fill it. The same problem is found on the API Specs page and elsewhere.

We decided to make our own empty states which help you understand what the page is for, and link to documentation to get you started faster.

api specs page sad view