Finish writing copy for the Open Data portal intro

[bminortx]

Find the google doc here: https://docs.google.com/document/d/1WVNTnZzSF7hPYMVumULvsoE1VC-X6WKn56e_9bFTcX0/edit?usp=sharing

It should be transferred to a markdown file eventually, but this is a great place to start.