use attachShadow "close" mode

[azu]

editor/packages/textchecker-element/src/text-checker-popup-element.ts

Line 103 in 270b400

const shadow = this.attachShadow({ mode: "open" });

[azu]

I've fixed it in ed22ab0, but it still affected by website's style.
Why?

https://html-coding.co.jp/annex/dictionary/html/textarea/