Gracefully map unknown or invalid Input.Key to ImGuiKey.None. (dotnet#2458)

* start of ImGui unknown key mapping fix.

* Gracefully map invalid `Input.Key` to `ImGuiKey.None`.

Author: Tweety-Lab

src/OpenGL/Extensions/Silk.NET.OpenGL.Extensions.ImGui/ImGuiController.cs

@@ -287,7 +287,6 @@ internal void PressChar(char keyChar)
         /// </summary>
         /// <param name="key">The Silk.NET.Input.Key to translate.</param>
         /// <returns>The corresponding ImGuiKey.</returns>
-        /// <exception cref="NotImplementedException">When the key has not been implemented yet.</exception>
         private static ImGuiKey TranslateInputKeyToImGuiKey(Key key)
         {
             return key switch
@@ -409,7 +408,7 @@ private static ImGuiKey TranslateInputKeyToImGuiKey(Key key)
                 Key.F22 => ImGuiKey.F22,
                 Key.F23 => ImGuiKey.F23,
                 Key.F24 => ImGuiKey.F24,
-                _ => throw new NotImplementedException(),
+                _ => ImGuiKey.None,       // Key isn't implemented
             };
         }