Fix sluggish Youtube Chat

// ==UserScript==
// @name         Youtube chat
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        https://www.youtube.com/live_chat*
// @grant        none
// @require      http://code.jquery.com/jquery-latest.js
// ==/UserScript==

$(function() {

    // Select the node that will be observed for mutations
    const targetNode = document.getElementById('contents');

    // Options for the observer (which mutations to observe)
    const config = { childList: true, subtree: true };

    // Callback function to execute when mutations are observed
    const callback = function(mutationsList, observer) {
        // Use traditional 'for loops' for IE 11
        for(const mutation of mutationsList) {
            if (mutation.type != 'childList')
                continue;
            // so we don't end up in an endless loop when modifying
            // the src attribute.
            if (mutation.addedNodes.length == 0)
                continue;
            for(const node of mutation.addedNodes) {
                if (node.src != null && node.src.endsWith('svg')) {
                    node.src = node.src.replace(/svg$/, 'png');
                }
            }
        }
    };

    // Create an observer instance linked to the callback function
    const observer = new MutationObserver(callback);

    // Start observing the target node for configured mutations
    observer.observe(targetNode, config);
});