(thanks to yuma140902) fixing issue with maximized windows.

What's New?
- Fixed issue where the addon doesn't work for some users.
- Addon will minimize faster (there was 200 ms delay).
- Ensure compatibility with Thunderbird v91.

Known Issues:
- Thunderbird icon in tray may disappear if you have the "move to tray when minimized" option enabled in the preferences, this is an issue from TB itself and nothing I am aware of can be done about it.

Fixed an issue where some addons might interfere with the minimizer.

Added a small delay before the window minimizes so that it can work on slower systems.