Merge feature SOL-20

This is a pull request to merge the SOL-20 feature (https://openedx.atlassian.net/browse/SOL-20).
In line 4 we include an image (thumbnail). We absolutely need to include an ALT attribute here:
<img src="<%= thumbnail %>" alt="">
When this image is originally uploaded, is a description added? the ALT attribute should include the description, if available, if not "No description available"