Adds link to MIT Libraries Dataverse to more tab

** Why are these changes being introduced:

* The "More..." tab of the multisearch widget does not have a link to
  our Dataverse instance, and we want that link to be there.

** Relevant ticket(s):

* https://mitlibraries.atlassian.net/browse/pw-97
* https://mitlibraries.atlassian.net/browse/PPD-165

** How does this address that need:

* This adds the link to the template for the "More..." tab.

** Document any side effects to this change:

* This plugin uses hard-coded templates for the four options, and also
  still has the variants from when we were using EDS rather than Primo.
  I'm choosing to leave all that in place for now, but it might make
  sense to clean this out during a future maintenance period.

web/app/plugins/mitlib-multisearch-widget/templates/tab-more-alma.php

@@ -17,6 +17,7 @@
 			<li><a href="/theses">MIT theses</a></li>
 			<li><a href="https://dspace.mit.edu">DSpace@MIT</a></li>
 			<li><a href="https://archivesspace.mit.edu/">ArchivesSpace</a></li>
+			<li><a href="https://dataverse.harvard.edu/dataverse/mit-libraries">MIT Libraries Dataverse</a></li>
 			<li><a href="http://libraries.mit.edu/experts/">Search tools by subject</a></li>
 			<li><a href="/search">More search options: images, data, etc.</a></li>
 		</ul>