Support serializing structs back into query strings

[nonnorm]

Hello!

Thank you for creating this crate, I really like the support for a variety of methods to handle arrays/nested structs.

I wanted to suggest adding support for serialization as well. It would be fantastic if the crate could take any struct that implements Serialize and convert it back into a query string format, respecting the different parsing modes. This would put it on par with other crates like serde_urlencoded.

[pooyamb]

@ravenclaw900 Thanks for bringing this up. I currently don’t have the capacity to work on implementing serialization, and I’d prefer not to unless it can match the deserialization side in terms of quality, testing, and performance. That said, I’m open to ideas. I gave it a shot before using the same mid-level structures but couldn’t come up with a design or API I was happy with. I'll keep this issue open just in case someone else wants to step up.