Added resource classses and a missing converter.

Harmonia.WinUI/Resources/ViewModels.xaml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<ResourceDictionary
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:vm="using:Harmonia.WinUI.ViewModels">
+
+    <vm:ViewModelLocator x:Key="Locator" />
+
+</ResourceDictionary>