Update dependencies and use new Rust edition

[TD-Sky]

This library fits my needs perfectly and I'm impressed with your solid work.

I make it evolve to modern rust: replacing the depreciated APIs and using the new features in Rust 2021.

I noticed you have been inactive on Github for a long time so I'm worrying about your status.
I have to apologize because I will create a new crate if you don't reply before next Monday (UTC).

[Odoh]

Oh, sorry for missing this. I was preparing for the Advent of Code this year, finally checking GitHub, and saw this.

That's great you found the library useful, and thank you very much for the updates!

Do you suggestions on what the best path forward is? I see you have several great, additional updates on your fork which are being published. Would it be best to deprecate this crate and defer to "-ng", or pull in all the updates here (I can give you full access to the repository)?

The other feature I considered adding was support for Calendar Events, parsing a calendar event expression and returning an iterator of chrono constructs.

[TD-Sky]

Happy to hear that you are fine!

I published the fork crate for cantino/mcfly#374 .

About the future of chrono-systemd-time

I think it enough to implement the whole standard. I considered adding timezone parsing support but I haven't examined the idea yet.

However, I'm preparing for my graduation (2024.06) and looking for job. So I'll probably be busy for a while. I may not be able to contribute to this project in time.

The first thing we could do

In my opinion, it's better to maintain the upstream crate when we have the same view. I can port back my code here and then archive -ng if you agree.

[Odoh]

Congratulations on the upcoming graduation!

In my opinion, it's better to maintain the upstream crate when we have the same view. I can port back my code here and then archive -ng if you agree.

Sounds good to me. I added you as a contributor to the repository, and I'll merge in this pull request and keep an eye out for more.

Thank you!