Add support for number ranges

[Ztry8]

This PR implements #601: support for number ranges in RON.

It's just syntactic sugar for structures with fields start, end or start, last.
It supports both std::ops and core::range.

Example:

let ranges = RangeTest {
    a: 0..5,
    b: 1..=3,
    c: 0.6..4.3,
    d: 0.3..=5.7,
};

let ser = ron::to_string(&ranges).unwrap();
assert_eq!(ser, "(a:0..5,b:1..=3,c:0.6..4.3,d:0.3..=5.7)");

let de: RangeTest = ron::from_str(&ser).unwrap();
assert_eq!(de, ranges);

[juntyr]

Thanks @Ztry8 for prototyping this feature!

[juntyr]

Also, this addition will need to be documented in the grammar

[Ztry8]

Thank you! I've already started working about this

[Ztry8]

@juntyr, is everything fine now? What should I put into CHANGELOG.md? Is the grammar.md correct?

[juntyr]

Thank you for the changes, I left some further comments

[Ztry8]

Thank you! l've already started to working on this

[Ztry8]

@juntyr, I’m happy with the work we’ve done, thank you very much!

I’ve implemented all of your suggestions & fixed CI.
Could you please check?

[Ztry8]

@juntyr, thanks for the corrections, I didn't notice them
What do you think now?

[juntyr]

We're on the home stretch now - there's also a conversation from earlier on about moving the number deserialiser that I unresolved - please have a look at that as well

[Ztry8]

Thanks! l've already started to working on this
Sorry about the number deserializer, I didn't understand what I needed to do at first

[Ztry8]

@juntyr, many thanks!

I've improved the tests, added more clarification in the comments, and moved the number deserializer

[juntyr]

@Ztry8 Thanks, we're almost almost there - thank you so much for making all these final adjustments

[Ztry8]

@juntyr, thank you for your help and cooperation!
I'm glad I can help make RON better, and I'm really happy with the progress we've made!

What's left to do?

[Ztry8]

@juntyr, what do you think now?

[Ztry8]

@juntyr, what do you think now?

[juntyr]

@Ztry8 Thank you so much for your amazing work on this feature! I've now merged the PR.

Let's give the PR a few days on main to try it out, and then I'll release a new version with the feature (feel free to ping me if I forget).

[Ztry8]

@juntyr, thank you for your help and cooperation!
I'm glad I can help make RON better, and I'm really happy with the progress we've made!