Add a recipe involving leap seconds to the cookbook

[ByteEater-pl]

Although it was decided this API doesn't support leap seconds, there are use cases requiring it, so it's a valid question how to make good use of Temporal manually combining it with a source of leap second timestamps. One or more such examples would be nice to have in the documentation.

[ryzokuken]

I attempted to get leap seconds support with the help of a custom 3rd party timezone in https://github.com/ryzokuken/temporal-tai. That said, IIRC, @gibson042 pointed out that the package might not be usable. If you could try it out and help me find out any potential issues, that would bring us closer to a well-known solution to the leap seconds problem.

[ByteEater-pl]

From a cursory overview of temporal-tai, both before and after filing this issue, I see no issues with it, but if I find any, I'll try to remember to report them. I'm curious what @gibson042's point was.

Your package uses t-a-i which contains hardcoded data about leap seconds in tai-data.js. So, naturally, jus as other solutions, it needs updating. So does leapseconds-announced, a library in the Haskell ecosystem from which I took inspiration, providing a value of type LeapSecondMap in the most popular time library, which supports a lot out of the box, but of course it cannot know leap seconds in advance, therefore an external source is needed for functions accepting values of type LeapSecondMap. I think it would be nice to have in the Temporal API itself: you pass the data about leap seconds and you get calculations taking them into account; barring this, a recipe or two is what I wish for with this issue.

[ptomato]

Thanks for the feedback, agreed that this should belong in the documentation. We have #900 open for this, so I'll close this one as a duplicate.