MvxTabbedPage Internal viewModel how to switch the currently selected tab
## 💬 Questions and Help

I want to switch tab toCharacteristic Details after clicking on the ChangeTab in the ServiceList page, how should I do it?

`
<?xml version="1.0" encoding="utf-8" ?>
<views:MvxTabbedPage x:TypeArguments="viewModels:DeviceDetailViewModel" 
             xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="http://schemas.android.com/apk/res/Collections.Droid"
             xmlns:Mvx="clr-namespace:MvvmCross.Forms.Views;assembly=MvvmCross.Forms" 
             xmlns:views="clr-namespace:MvvmCross.Forms.Views;assembly=MvvmCross.Forms"
             Title="{Binding Title}"
             x:Class="UnionDeviceApp.UI.Pages.DeviceDetailPage">
    <views:MvxTabbedPage.Children>
        <ContentPage Title="ServiceList">
            <Button Text="ChangeTab" Command="{Binding ChangeTab}"></Button>
        </ContentPage>
        <ContentPage Title="Characteristic Details">
            
        </ContentPage>
    </views:MvxTabbedPage.Children>
</views:MvxTabbedPage>
`

