[v3 mac] Add IsDarkMode to application and JS runtime. Add Common.ThemeChanged event

v3/pkg/application/messageprocessor.go

@@ -94,6 +94,8 @@ func (m *MessageProcessor) HandleRuntimeCall(rw http.ResponseWriter, r *http.Req
 		m.processScreensMethod(method, rw, r, targetWindow, params)
 	case "call":
 		m.processCallMethod(method, rw, r, targetWindow, params)
+	case "system":
+		m.processSystemMethod(method, rw, r, targetWindow, params)
 	default:
 		m.httpError(rw, "Unknown runtime call: %s", object)
 	}