Added respective methods to IView and GLFW and SDL windows

Author: mayatskiy

src/Windowing/Silk.NET.Windowing.Common/Interfaces/IView.cs

@@ -103,6 +103,11 @@ public interface IView : IViewProperties, IGLContextSource, IVkSurfaceSource, ID
         /// </summary>
         void Reset();
 
+        /// <summary>
+        /// Sets focus to current window.
+        /// </summary>
+        void SetFocus();
+
         /// <summary>
         /// Close this window.
         /// </summary>

src/Windowing/Silk.NET.Windowing.Common/Internals/ViewImplementationBase.cs

@@ -71,6 +71,7 @@ protected ViewImplementationBase(ViewOptions opts)
         public abstract void ContinueEvents();
         public abstract Vector2D<int> PointToClient(Vector2D<int> point);
         public abstract Vector2D<int> PointToScreen(Vector2D<int> point);
+        public abstract void SetFocus();
         public abstract void Close();
         protected abstract void RegisterCallbacks();
         protected abstract void UnregisterCallbacks();

src/Windowing/Silk.NET.Windowing.Glfw/GlfwWindow.cs

@@ -631,6 +631,11 @@ public bool TryGetProcAddress(string proc, out nint addr, int? slot = default)
             return ret;
         }
 
+        public override void SetFocus() 
+        {
+            _glfw.FocusWindow(_glfwWindow);
+        }
+
         public override void Close()
         {
             Closing?.Invoke();

src/Windowing/Silk.NET.Windowing.Sdl/SdlView.cs

@@ -283,6 +283,11 @@ internal void RemoveEvent(int index)
             Reset();
         }
 
+        public override void SetFocus()
+        {
+            Sdl.RaiseWindow(SdlWindow);
+        }
+
         public override void Close()
         {
             Closing?.Invoke();