[One Pager] Create a one pager for org Account numbers

The Organization Account Numbers page does not have a one-pager right now. It'd be handy to add that since most other organization pages have one.

Start from the Organization Account Numbers page and compare it with the existing one-pagers for other organization pages. Add the missing one-pager in the same location and style, then verify that it appears consistently with the other organization pages.

Written by the indexing model from the issue text.