LP#1433328: Add class attribute to e-resource links in TPAC

LP#1433328: Add class attribute to e-resource links in TPAC

In the TPAC, links to electronic resources are not directly, uniquely
identifiable in the DOM. You can specify these links indirectly, with
something like '.result_table_title_cell > td > a' in search results
or '.rdetail_uri > a' on the record details page, but this is fragile
and a bit cumbersome. Adding a unique class attribute directly to the
link elements would make things easier for services built on top of
the TPAC, such as Overdrive API integration or JS-based analytics for
e-resources.

Signed-off-by: Jeff Davis <jdavis@sitka.bclibraries.ca>
Signed-off-by: Josh Stompro <stomproj@larl.org>
Signed-off-by: Ben Shum <bshum@biblio.org>