fix examples and readme

MiraAPI.Example/ExampleAssets.cs

@@ -0,0 +1,9 @@
+using MiraAPI.Utilities.Assets;
+
+namespace MiraAPI.Example;
+
+public static class ExampleAssets
+{
+    public static LoadableResourceAsset ExampleButton { get; } = new("MiraAPI.Example.Resources.ExampleButton.png");
+    public static LoadableResourceAsset Banner { get; } = new("MiraAPI.Example.Resources.FortniteBanner.png");
+}