The collaborative annotation is available HERE. The site allows you to view key papers and documents, see the annotations of other users, and add your own annotation. You can also add new documents to the library. NOTE: this site, as currently configured requires a computer or tablet. It is not fully functional on a mobile phone.
Note that you will need to create an account to be able to add and annotate papers. A User Guide can be found HERE.
This site is also enabled for Hypothes.is. If you are a Hypothes.is user, install the browser extension and send an email to thesciencecollaborative@gmail.com to request membership in the science collaborative group. A Zotero shared library is coming soon.