Serde feature

[Weasy666]

Hi there!
Let me thank you first for creating this crate.

Then i'd like to ask you, if there are any plans to add a serde feature which allows to de-/serialize the country codes?

[zhangjiayin]

Hi ,
Thank you for your interest in contributing!
While we haven't prioritized Serde support for country codes yet,
your contribution would be highly welcomed.
Feel free to submit a PR.