fix: alert running session at wrong state

The countdown has not set `isPaused` value to `true` when it ends. This alerts user of running session when they close the website even though the countdown is not running. This commit addressed that.

Author: hecticme

src/composables/usePomodoro.js

@@ -129,6 +129,7 @@ export default function usePomodoro () {
 
     playNotificationSound()
     clearCountdownInterval()
+    isPaused.value = true
     pomodoro.setIsBreak(false)
 
     document.title = 'Simplemodoro'