[Visual Improvement] Add a dark scrollbar for chrome & safari

[LilyKensa]

As the title says, when using chrome, we got a very white scrollbar that conflicts a lot with the website's style.

I hope we got something like this instead:

My CSS code:

body::-webkit-scrollbar {
    width: 12px;
    height: 12px;
}

body::-webkit-scrollbar-thumb {
    background-color: #515151;
    border-radius: 10px;
    border: 2px solid transparent;
    background-clip: content-box;
}
body::-webkit-scrollbar-thumb:hover {
    background-color: #5b5b5b;
}
body::-webkit-scrollbar-thumb:active {
    background-color: #6d6d6d;
}

body::-webkit-scrollbar-track {
    background-color: #161616;
}