setup android project

Raylib-cs.Android/MainActivity.cs

@@ -0,0 +1,13 @@
+namespace Raylib_cs.Android;
+
+[Activity(Label = "@string/app_name", MainLauncher = true)]
+public class MainActivity : Activity
+{
+    protected override void OnCreate(Bundle? savedInstanceState)
+    {
+        base.OnCreate(savedInstanceState);
+
+        // Set our view from the "main" layout resource
+        SetContentView(Resource.Layout.activity_main);
+    }
+}