feat: show time saved (effective playback rate) on the icon badge

[WofWca]

Like this:

The code where the badge is updated:

jumpcutter/src/entry-points/background/iconAndBadgeUpdater.ts

Lines 25 to 26 in 005265b

 browser.browserAction.setBadgeBackgroundColor({ color }); 
 browser.browserAction.setBadgeText({ text });