Add new lives mode and more test options!

Users can now choose from two modes - lives and questions. Lives mode will end when the user makes the chosen number of mistakes. Questions mode will end when the user answers all questions correctly from a list of questions the length of which the user chooses.

src/CountdownTestStart.js

@@ -0,0 +1,16 @@
+import React from "react";
+
+export default function CountdownTestStart(props) {
+	return (
+		<>
+			<div className="overlay" onClick={props.hideTestStart}></div>
+			<div className="overlay-content options-list-overlay-content">
+				Awaiting content
+
+				<div onClick={props.hideTestStart}>
+					Cancel
+				</div>
+			</div>
+		</>
+	)
+}