Set Aside Tabs troch kuangkuang

This is a copy of Edge feature: set aside tabs, whis is a very useful feature to organize tabs and work spaces. Since firefox doesn't have it, I created this addon to introduce the feature.

Features:

• Collect all the open tabs and set them aside
• If there is any highlighted tabs, collect highlighted tabs is possible
• The set aside tabs are shown in the addon page with titles and page snapshots
• Restore set aside tabs later
• Give names to set aside tabs
• Set aside tabs are synced via firefox account
• Shortcut command (default Alt + Shift + U) is available for fast action. The shortcut can be changed in firefox addon management page (about:addons)

Differences from Edge feature:

• Because the firefox sidebar is too narrow for the feature, I put the set aside tabs in a separate tab.
• It only set aside normal tabs that is not pinned, so if the firefox preference page is open, it is not set aside.
• Bookmark function is not included. I don't think it is very useful. If you think so, let me know.