[docs] Document NativeAOT support. Fixes dotnet#18585.

Fixes dotnet#18585.

docs/nativeaot.md

@@ -0,0 +1,49 @@
+# NativeAOT
+
+We've added *experimental* support for using [NativeAOT][1] when publishing iOS,
+tvOS, Mac Catalyst and macOS apps in .NET 8.
+
+NativeAOT may produce smaller and/or faster apps - or it may not. It's very
+important test and profile to determine the results of enabling NativeAOT.
+
+NativeAOT is enabled by setting the `PublishAot` property to `true` in the project file:
+
+```xml
+<PropertyGroup>
+	<PublishAot>true</PublishAot>
+</PropertyGroup>
+```
+
+## Notes
+
+NativeAOT is only used when publishing (`dotnet publish`). In particular
+`dotnet build -t:Publish` is _not_ equivalent to `dotnet publish`, only
+`dotnet publish` will enable NativeAOT.
+
+**Unsupported** workaround: set the `_IsPublishing` property to `true` to make
+`dotnet build` think it's `dotnet publish`:
+
+```xml
+<PropertyGroup>
+	<PublishAot>true</PublishAot>
+	<_IsPublishing>true</_IsPublishing>
+</PropertyGroup>
+```
+
+This can be useful to install and run apps with `NativeAOT` from the IDE,
+because it's not possible to use `dotnet publish` when running from the IDE.
+
+Note that NativeAOT does not support managed debugging.
+
+There's no interpreter when using NativeAOT, and as such the `UseInterpreter`
+and `MtouchInterpreter` properties have no effect.
+
+NativeAOT requires trimming, and `MAUI` isn't trimmer-safe, and thus
+unfortunately `MAUI` projects don't typically work with NativeAOT (we hope to
+rectify this situation for .NET 9).
+
+There are no known issues specific to our platforms with NativeAOT; but the
+[limitations][2] are exactly the same as for other platforms.
+
+[1]: https://learn.microsoft.com/en-us/dotnet/core/deploying/native-aot
+[2]: https://learn.microsoft.com/en-us/dotnet/core/deploying/native-aot/?tabs=net8plus%2Cwindows#limitations-of-native-aot-deployment