v1.3.4: Fix accidentally closing new tab when there's no duplicate

Fixed handling of links with # at the end, which broke certain functionality on some sites (like Reddit).

Added notifications to give visual feedback.

Notifications can be clicked to switch to newly created tabs or to return to the previous tab (in certain situations).

Support for intentional duplicate tabs has been added, but not all use cases are handled yet.

Refactor and handled some edge-cases