Mm/ops data api readme (#668)
Mm/ops data api readme (#668)

* DA-591 add readme file

* DA-591 add info

* DA-591 add links and more info

* DA-591 remove internal links

* DA-591 remove the rest of the links

all-of-us/raw-data-repository,all-of-us/raw-data-repository,all-of-us/raw-data-repository