Repository in discussions list should link to the actual repository

Created by: slimsag

In https://github.com/sourcegraph/sourcegraph/pull/1824 @francisschmaltz added the repository to the discussion lists we have, e.g. on https://sourcegraph.com/discussions

Every other sub-item in these lists is clickable or interactive in some way: you can click the author, you can hover over the timestamp and comment counts.

The repository portion of the list item should be a link that goes to the repository on Sourcegraph.