Tag Helper initializers

[DamianEdwards]

Enable any Action<ITagHelper, ViewContext> to be registered in DI to allow setting of tag helper properties after any [Activate] properties are set but before their bound from the source document and the tag helper is executed.

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.InitializeTagHelper<FormTagHelper>((helper, viewContext) =>
        {
            helper.AntiForgery = false;
        });
    }

    ...