rawinput: add basic support for xinput (#617)

## Link to GitHub Issue or related Pull Request, if one exists
#616 

## Description of change
Adds preliminary support for XInput controllers. Enough to manually bind
buttons and map analogs.

src/spice2x/overlay/windows/control.cpp

@@ -732,6 +732,10 @@ namespace overlay::windows {
                             ImGui::Text("Type: PIUIO");
                             break;
                         }
+                        case rawinput::XINPUT_GAMEPAD: {
+                            ImGui::Text("Type: XInput");
+                            break;
+                        }
                         case rawinput::DESTROYED: {
                             ImGui::Text("Disconnected.");
                             break;