Add button linking pseudoknot training collection to lab carousel slide

[tkaragianes]

The API response for labs doesn't include any options for specifying training collections, so until we add a feature for something like that, I've hardcoded a training collection button into the lab slide that directly links to the correct collection. It will only display for the pseudoknot lab now, but in the future we may want to add more options for associating training collections with a given lab.

[tkaragianes]

Yeah, I figured we could address it in the API rewrite.