TypeExtensions properties

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Since C# doesn't support extension properties it is possible to introduce extension methods working for all frameworks like it is done in: https://github.com/rsdn/CodeJam/blob/master/CodeJam.Main/Targeting/TypeExtensions.cs

Example for IsSealed

		[MethodImpl(AggressiveInlining)]
		public static bool GetIsSealed([NotNull] this Type type) =>
#if TARGETS_NET || NETSTANDARD20_OR_GREATER || NETCOREAPP20_OR_GREATER
			type.IsSealed;
#else
			type.GetTypeInfo().IsSealed;
#endif

Another option is to make a class wrapper.