exp/textinput: bug fix: don't send events on Enter on desktop browsers

Apparently sending an event on pressing Enter on desktops could sometimes
duplicate texts.

Closes #3041

exp/textinput/textinput_js.go

@@ -78,7 +78,7 @@ func (t *textInput) init() {
 		if e.Get("code").String() == "Tab" {
 			e.Call("preventDefault")
 		}
-		if e.Get("code").String() == "Enter" || e.Get("key").String() == "Enter" {
+		if ui.IsVirtualKeyboard() && (e.Get("code").String() == "Enter" || e.Get("key").String() == "Enter") {
 			// Ignore Enter key to avoid ebiten.IsKeyPressed(ebiten.KeyEnter) unexpectedly becomes true.
 			e.Call("preventDefault")
 			ui.Get().UpdateInputFromEvent(e)