Comprehensively update user manual and contributor guide, add Adam to core team

website/static/js/video-autoplay.js

@@ -0,0 +1,21 @@
+const VISIBILITY_COVERAGE_FRACTION = 0.25;
+
+window.addEventListener("DOMContentLoaded", () => {
+	const players = document.querySelectorAll("[data-auto-play]");
+	players.forEach((player) => {
+		if (!(player instanceof HTMLVideoElement)) return;
+
+		let loaded = false;
+
+		new IntersectionObserver((entries) => {
+			entries.forEach((entry) => {
+				if (!loaded && entry.intersectionRatio > VISIBILITY_COVERAGE_FRACTION) {
+					player.play();
+
+					loaded = true;
+				};
+			});
+		}, { threshold: VISIBILITY_COVERAGE_FRACTION })
+		.observe(player);
+	});
+});