FIX: VroomJS engine initialize failed on macOS.

[holmesconan]

#338 mentioned this error, and as the chakra js engine already added, which support osx-x64 platform, I think the simplest way is to skip the VroomJS engine if it is not available. And the fix is also a defensive programming for this situation.

[Daniel15]

People still using .NET Framework 4.0 or 4.5 on Linux (via Mono) still need to see the VroomJs initialisation error, though.

Instead of doing it this way, you can modify your app to only add the Chakra engine rather than VroomJs. Just configure the engines before calling UseReact:

var engineSwitcher = JsEngineSwitcher.Instance;
engineSwitcher.EngineFactories
    .AddChakraCore();

app.UseReact(config =>

[dustinsoftware]

Thanks for the PR. Unfortunately this isn't mergeable as-is and hasn't had any recent activity, so I'm going to close this for now. Please feel free to re-open when you'd like to revisit this.