Added dark theme CSS and automatic theme switching based on OS/browser settings

Author: royborgen

radicale/web/internal_data/index.html

@@ -12,7 +12,8 @@
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <meta http-equiv="X-UA-Compatible" content="IE=edge">
   <title>Radicale Web Interface</title>
-  <link href="css/main.css" type="text/css" media="screen" rel="stylesheet">
+  <link href="css/main.css" rel="stylesheet" media="(prefers-color-scheme: light)">
+  <link href="css/main-dark.css" rel="stylesheet" media="(prefers-color-scheme: dark)">
   <link href="css/icon.png" type="image/png" rel="icon">
   <script type="module" src="js/main.js"></script>
 </head>
@@ -407,4 +408,4 @@ <h1 data-name="headertitle">Delete Collection</h1>
   </main>
 </body>
 
-</html>
+</html>