begin converting WakatimeCore

src/popup.tsx

@@ -1 +1,14 @@
-// Stub for port of previous extension
+import React from 'react';
+import ReactDOM from 'react-dom';
+const container = document.getElementById('wakatime');
+
+const openOptions = async (): Promise<void> => {
+  await browser.runtime.openOptionsPage();
+};
+ReactDOM.render(
+  <>
+    <h1>POPUP GO HERE</h1>
+    <div onClick={openOptions}>Open options</div>
+  </>,
+  container,
+);