History ADV+ troch libReads

This add-on allows user to keep track of all of the websites they visited while preserving useful metadata, such as:
- focus of every tab
- events associated with tab: update, remove, create
- flag trackers for audible and mute
- unix timestamp for all events
User can access the history by clicking on add-on icon. On the add-on page user can also choose to export all history in a .csv file

Known issues (soon to be resolved):
- The page history becomes unresponsive and doesn't display all items
- After about 68 thousand entries (averages 23 days) plugin stops recording new events