Add skipping tests based on the [SupportedOSPlatform] attribute

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Adding support for SupportedOSPlatform is great because this attributes suppresses the CA1416 code analysis warning.

This feature was requested in xunit/xunit#2820 but was not implemented in xUnit.net

Important

I documented in the README that this feature is available since version 1.5. Please update the README to match the actual version number of the next release.

Ping @sliekens who might be interested in this feature. 😉

[AArnott]

Looks amazing! Thank you.

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Awesome, thanks for merging! Do you plan to release a new (1.5) version on NuGet anytime soon?

[AArnott]

Yes, with your addition I think I'll push the release today.

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I see that version 1.5.22-g0ae9b5ba5c was released. Did you actually mean to publish a prerelease? I read a bit about Nerdbank.GitVersioning, especially Public vs. stable releases and version.json file but I must admit that as a MinVer user I'm a bit lost. 🤨

[AArnott]

Ah phooey. I meant it to be stable. I changed my release process and apparently there's a bug. I'll get that fixed and re-release.

[sliekens]

I also highly recommend MinVer, though I never tried Nerdbank.GitVersioning, it's very hard to make a mistake with MinVer.

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@sliekens Something tells me that Andrew is going to stick with Nerdbank.GitVersioning. 😉

And thanks @AArnott for releasing version 1.5.23! 🥳

[sliekens]

Oh well. I said what I said. All I can do now is double down on it.

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And I just opened the first pull request ever to use this new feature! 🤓 MarkusPalcer/blurhash.net#28

[AArnott]

Oh! I hadn't noticed that it works when the SupportedOSPlatform attribute is added to the test class as well. Very cool.
We should call that out on the doc page.

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I documented this behaviour in the private TestMethodExtensions.GetPlatforms method which is admittedly not the most discoverable place. 😆