Maintenance status

[aumetra]

First off, thank you for this crate. It really made it easy to adopt JSON Schema for some of my projects.

However I noticed that the reviewing of PRs has slowed down over time.
I feel like there are multiple PRs which would directly and indirectly benefit consumers of the crate

Some of the PRs I'd see value in, even before the API redesign drops, are:

• Update to syn 2.0, and serde_derive_internals 0.29 #269
• simplify the code generated for unit, externally tagged and internally tagged enums #266

If there's a lack of time or motivation (both of which I totally get), I'm willing to help with maintenance (at least to the extent I'm able to time and skill-wise).

[chenyukang]

@GREsau Thanks for your awesome project.
Our project also relies on this crate, it's great if someone could help to maintenance this crate.