Make this library trimmable #164

Description

I am using this library in blazor wasm application, but this library's bundle size is 357kb. Which is a lot for a web application.
I also created similar ticket for FSharp.Data.Adaptive, which they already made it hanppen. fsprojects/FSharp.Data.Adaptive#104
And the result is pretty good.

Known workarounds

People can add below stuff to their own application to make it work. But it is better to have it support by default.

<Target Name="ConfigureTrimming" BeforeTargets="PrepareForILLink">
<ItemGroup>
	<ManagedAssemblyToLink Condition="'%(Filename)' == 'FSharp.Control.Reactive'">
		<TrimMode>link</TrimMode>
		<IsTrimmable>true</IsTrimmable>
	</ManagedAssemblyToLink>
</ItemGroup>
</Target>