Impl JsonSchema for Date/Time

[ralpha]

Rocket uses Date and Time as shown here https://docs.rs/rocket/0.5.0-rc.1/rocket/form/trait.FromFormField.html#impl-FromFormField%3C%27v%3E-for-Date in it internal implementations and exposes them to be used.

Schemars does not implement JsonSchema for them yet.
But note that Rocket might update them to time 0.3.2 in the future. So maybe just implement them for 0.3.2 immediately.

[ittorchbearer]

I believe I have this and DateTime implemented on my repo: https://github.com/Plato-solutions/Rocket
Not enough time to get pull requests out atm. https://github.com/Plato-solutions/Rocket

[kontsaki]

Hello, is this still relevant and something worth creating a PR for? Since Rocket now uses time and also it seems time is a relevant lib again.