make entire 'view on' line be link, to match Youtube and for a11y.

This doesn't have a ticket because this is just something I noticed - can you make sure I've fixed it correctly?

Youtube was done as "view on Youtube", which is the right pattern, as "view on Facebook" is not very accessible (it gives no context to what you're doing on Facebook). This branch should make all the embeds follow the "view on thing" format.