[improvement] Click "# reply/replies" button to close discussion sidebar

[improvement] Close discussion sidebar with click on the same "# reply/replies" button in the main chat.
Edit: I now see that the thing that adds the button and sidebar is called "Reply in Thread".

• This would greatly improve usability and speed of the discussion sidebar.
• You now have to move your mouse and click on the tiny "X" in the top right corner of the sidebar, then find your place again in the main chat. With this improvement, your mouse could remain where you were reading.
• Please retain current behavior to open an other discussion in the sidebar when you click on a different "# reply/replies" in the same chat.
• This would be useful in any version (web/installed).
• (Possibly also add a keyboard shortcut to close the discussion sidebar. E.g.: Shift+F4 or Escape)
• (Possibly allow keyboard scrolling within sidebar (without having to move the mouse there first). E.g.: Shift+Up/Down).

No file or test is named. Start by locating the TypeScript implementation of the “Reply in Thread” button and discussion sidebar, then reproduce opening a thread from the main chat. Done means clicking the same reply button closes the sidebar while clicking a different reply count opens that discussion, without disrupting the web or installed experience.