Make the countdown timer accessible through the API

[tobiasvl]

It would be nice if the timers were accessible through the API; time until next jam, time until submission, and time until play+rate closes.

(Unless this already is available?)

[zwrawr]

You can see the start and end of the weekend here https://api.ldjam.com/vx/node/get/{event_id}?pretty (e.g. https://api.ldjam.com/vx/node/get/139254?pretty)

but you cannot get other dates from the api because they are hardcoded here https://github.com/ludumdare/ludumdare/blob/master/src/com/view/sidebar/sidebar.js#L17