rename test.html to index.html, add UTF-8 meta tag to index.html

lightweight_charts/js/index.html

@@ -5,6 +5,7 @@
     <link rel="stylesheet" href="styles.css">
     <script src="./lightweight-charts.js"></script>
     <meta name="viewport" content ="width=device-width, initial-scale=1">
+    <meta charset="UTF-8">
     <style>
     body {
         margin: 0;