Add a link to the LMS privacy policy to the "Getting started" window for LMS users.

**The issue**
Per our new HECVAT answers, we need a better way of pointing end users of the LMS app towards our LMS privacy policy (https://web.hypothes.is/privacy/lms/), since they can easily launch our app without ever touching our web site.

**Possible solution**
The quickest win here might be to include the Privacy Policy link in the Getting Started window that's open the first time a user launches our app. We should make sure the LMS PP link only shows up for LMS users.

Locate the Getting Started window and the logic that identifies LMS users. Review how first-launch content and external links are presented, then add the LMS privacy policy link only for those users. Done means the link appears in the first-launch window for LMS users and is absent for other users.

Written by the indexing model from the issue text.