feat(toolbar): Adds custom badge for Safari

[ERosendo]

This PR addresses a few issues related to the badge introduced in #379, specifically for Safari.

While running the QA steps, I found the following issues:

• Safari doesn't render emojis inside the badge like Firefox and Chrome.
• Badge background color customization is not supported. It's always red. This issue is documented in the MDN web docs, here's the link: setBadgeBackgroundColor()-Mozilla | MDN
• The current approach to remove the badge after users close the popup window is not working in Safari. This issue is also reported here: port.onDisconnect is not fired when connection is broken lapcat/SafariExtensions#40

This PR introduces the following changes:

• Adds logic to identify the Safari engine and uses an exclamation mark as a substitute for the bell emoji. Here's a screenshot of how it looks:

• Implements a new event-based approach to remove the badge after the popup closes. This method sends a message to the background script upon popup closure, bypassing the port-based mechanism used for Chrome and Firefox. Here's a GIF showing the badge is properly removed in Safari