Improves the notification system

[Berkmann18]

This PR explores more ideal throttling/debouncing durations and add sounds too.

Notes:

• If we use throttling, it will conveniently notify the user, however, it may lead to some notifications being shown a period after the touch was detected.
• If we use rebouncing, it will notify promptly (so no delay problem compared to throttling) but it will only launch the notifications after the touch was detected (which may not be desirable in our case).
• I've left a comment on ui.js with what seemed to be the ideal delays.
• One more improvement that could be done is the use of the favicon or relevant image as the notification's icon/badge. However, some browsers (e.g. Vivaldi, Chrome, Chromium, Opera and Brave) are overriding it with their icons (unlike Firefox). No idea about Edge and Safari (both of which aren't available on ArchLinux).

Resolves #39

[Berkmann18]

Do we really want the "Stop it, get some help" audio? LOL it's kinda funny

I was aiming for a simpler sound like "Stop it" or "Put your Hands Down!" or something that would go along those lines. That being said, I thought that the "Stop it, get some help" wasn't too aggressive/authoritarian while being light-hearted, iconic and a bit humourous so I went with that while keeping a simpler blob sound (that could be used for other notifications later on).

There are probably better and more suitable sounds that would reinforce the notification's message but I couldn't find any in the brief time I spent looking for audio that would at least be good enough.