make sure all spec costs are available via JSON

[davewhiteland]

In the task 2-COST, it would be good if students could load cost data from the race server... but currently not all items' costs are included in the JSON. Would be good to review this and see if there is any reason why this can't be usefully/heplfully tabulated and exposed as helpful JSON data.

On demo site: see https://demo.buggyrace.net/specs/data — the values data is really just the enumerations, that happen to include cost. The cost data is available on that page, but not via a JSON call.