Improvements:

* Fix issue with blank popups

Features added:

* Tab Group add-on import

Improvements:

* More robust tabs to bookmarks sync
* Improved preferences styling
* Use Rollup.js for bundling

Initial version including the following features:

* Create empty group
* Save tabs of current window as new group
* Switch between groups
* Close the currently open group
* Changes made to tabs are persisted (tab created, url/title changed, tab closed, tab moved within window, tab moved between windows)
* Option panel to change the name of the root folder