Mention BinaryPrimitives on BitConverter page

I was completely unaware of the [BinaryPrimitives](https://docs.microsoft.com/en-us/dotnet/api/system.buffers.binary.binaryprimitives?view=net-6.0) class until just now and have been using [BitConverter](https://docs.microsoft.com/en-us/dotnet/api/system.bitconverter?view=net-6.0) but converting everything to little-endian. Another user was [also](https://github.com/dotnet/runtime/discussions/64953) unaware back in February. It seems like it could be advertised much better.

Could BinaryPrimitives be mentioned quite clearly on the BitConverter page (e.g. in a coloured info box)? It can be problematic having the conversion based on the machine's architecture, and it's probably not what most people want.