How to apply Shadow theme for rendering calendar within its own shadow DOM (added in v6.1.0)

Question

I recently used the FullCalendar with the WebComponent and I'm trying to use the Shadow Theme but I can't find the way to do it in the documentation with JavaScript. To add more context, the Shadow DOM appears here.

<div id='calendar'></div>

var calendar;
document.addEventListener("DOMContentLoaded", function () {
  var calendarEl = document.getElementById("calendar");
  calendar = new FullCalendar.Calendar(calendarEl, {
    aspectRatio: 3,
    initialView: "dayGridMonth",
    headerToolbar: {
      left: "prev,next today",
      center: "title",
      right: "dayGridMonth,timeGridWeek,timeGridDay",
    },
  });
  calendar.render();
});