v12 (#5712)

Co-authored-by: MeiMei <30769358+mei23@users.noreply.github.com>
Co-authored-by: Satsuki Yanagi <17376330+u1-liquid@users.noreply.github.com>

src/client/scripts/contains.ts

@@ -0,0 +1,9 @@
+export default (parent, child, checkSame = true) => {
+	if (checkSame && parent === child) return true;
+	let node = child.parentNode;
+	while (node) {
+		if (node == parent) return true;
+		node = node.parentNode;
+	}
+	return false;
+};