Highlighting in shadow DOM

With an option shadowDOM : true the advance-mark.js now is able to highlight inside shadow DOMs that have mode: 'open' and are already created.
You can play with advance-mark.js-playground. Examples -> Shadow DOM.
Note: to style mark elements in shadow DOM, the option shadowDOM : {style : 'your mark element style'} can be used.
It creates a style element and inserts it at the beginning of shadow root child node(s).
But this operation is invasive, it can break the root code.
An inline style can be used as an alternative:

each : (markElement, info) => {
  // a shadow root is the DocumentFragment
  if (markElement.getRootNode().nodeType === Node.DOCUMENT_FRAGMENT_NODE) {
    markElement.style.color = "red";
  }
}