Support for Chrono behind feature flag

[arthmis]

It would nice to have Data implemented for Chrono data types behind a feature flag. It's not very essential I think though.

[cmyr]

This is a tricky question. In theory there are an unlimited number of external types, and it's hard to determine what should qualify for inclusion for the purposes of Data. One concern is that this increases the cost of testing, since we want to test all features.

chrono feels like a reasonable thing to include, since it's so commonly used, and time is an important concept in a GUI. Especially since we will likely eventually ship a date picker, I think this makes sense.

[arthmis]

Yes for my case, it alleviates needing to implement Data manually for types that contain chrono types. It's not a problem, but just a bit annoying.