Add IApp & AppExtensions for accessing the properties & functions from anywhere in the application

Author: Jack251970

Flow.Launcher.Core/AppExtensions.cs

@@ -0,0 +1,15 @@
+using System.Windows;
+using Flow.Launcher.Plugin;
+
+namespace Flow.Launcher.Core;
+
+/// <summary>
+/// Extension properties and functions of the current application singleton object.
+/// </summary>
+public static class AppExtensions
+{
+    /// <summary>
+    /// Gets the public API of the current application singleton object.
+    /// </summary>
+    public static IPublicAPI API => (Application.Current as IApp)!.PublicAPI;
+}

Flow.Launcher.Core/IApp.cs

@@ -0,0 +1,13 @@
+using Flow.Launcher.Plugin;
+
+namespace Flow.Launcher.Core
+{
+    /// <summary>
+    /// Interface for the current application singleton object exposing the properties
+    /// and functions that can be accessed from anywhere in the application.
+    /// </summary>
+    public interface IApp
+    {
+        public IPublicAPI PublicAPI { get; }
+    }
+}