Make screenshot image clickable with Enlarge Screenshot button

[ssciolla]

Usability testing suggested that some users expect to be able to click the button to open the larger version of the image. The UX team suggested putting both the Enlarge Screenshot text and image inside a button.

TEST PLAN:

• Choose one LTI tool card, and click on the MORE button to expand the detailed view
• If there is a screenshot included in the Description field, click on the image
• Verify the pop up image with enlarged view of this screenshot. You can click on the "Close" button to close the window.

[roujiawang]

Investigated a few cards per TEST PLAN. No unexpected behavior found.