Add support for Xamarin.Android

[ackava]

[ClearScriptLib]

Closing as duplicate of Issue #9.

[ackava]

@ClearScriptLib Will .NetStandard work on Xamarin.Android? or will it only be specific to windows?

[ClearScriptLib]

@ackava .NET Standard is an API specification that Mono should support eventually if it doesn't already. However, ClearScript is unlikely to work on non-Windows platforms due to its reliance on mixed assemblies.