added extensive markdown rendering tests and Kotlin/JS externals for marked library

site/src/jsMain/resources/index.html

@@ -28,6 +28,11 @@
       integrity="sha384-QWTKZyjpPEjISv5WaRU9OFeRpok6YctnYmDr5pNlyT2bRjXh0JMhjY6hW+ALEwIH"
       crossorigin="anonymous"
     />
+    <!-- Bootstrap Icons -->
+    <link
+      rel="stylesheet"
+      href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.11.3/font/bootstrap-icons.min.css"
+    />
   </head>
   <body>
     <div id="root"></div>