play.js

function () {

	function waitForElementToAppear(selector, callback) {
		const element = document.querySelector(selector);
		if (element) {
			callback(element);
			return;
		}

		const targetNode = document.body;
		const config = { childList: true, subtree: true };
	
		const observer = new MutationObserver((mutationsList, observer) => {
			const element = document.querySelector(selector);
			if (element) {
				observer.disconnect();
				callback(element);
			}
		});

		observer.observe(targetNode, config);
	}

	console.log("Start");		
	waitForElementToAppear("#player audio", (button) => {
		console.log("Play!");
		button.play();
	});

}