Custom elements within the page should inherit the document's ::selection, ::target-text, ::highlight, ::spelling-error, ::grammar-error style by default, otherwise each custom element needs to be inherited manually.

example: https://codepen.io/mantou132/pen/mdvQMwz?editors=0110

Chrome current inherit: https://issues.chromium.org/issues/381335069 , but something strange:

Firefox not inherit: https://bugzilla.mozilla.org/show_bug.cgi?id=1868009