Update textbox classes and selectors

[Eir-nya]

Updates class selectors for the chat textbox.

Notes:

• Discord's previous use of #icon has been replaced with a class, .lottieIcon_f73ef7.
• Selector for Gif Button had to be specified using aria-label, otherwise the selector also targeted sticker and emoji buttons.
• This block

&:hover #icon svg {
    background: var(--interactive-normal);
}

had to be moved to within the Gif Button selector (now &:hover .lottieIcon_f73ef7 svg), otherwise this block also affected the Nitro gift button when hovering.

In these screenshots I have a few extra buttons, that's just some plugins from Vencord :)

Let me know if there's any problems!

Before:

After: