index: Add /de/ and /en/ versions

www/index.php

@@ -1,6 +1,23 @@
 <?php
 header("Content-Length: 0");
 switch ($_SERVER['PATH_INFO']) {
+    case '':
+    case '/':
+        $lang = 'de';  // prefer german
+        if (isset($_SERVER['HTTP_ACCEPT_LANGUAGE'])) {
+            foreach (explode(',', $_SERVER['HTTP_ACCEPT_LANGUAGE']) as $pref) {
+                $l = substr($pref, 0, 2);
+                if ($l === 'de') {
+                    $lang = 'de';
+                    break;  // force german
+                } else if ($l === 'en') {
+                    $lang = 'en';  // use english only, if user specifically asks for it
+                }
+            }
+        }
+        header("Status: 303");
+        header("Location: /$lang/");
+        break;
     case '/changelog':
         header("Status: 303");
         header("Location: https://git.necronda.net/winzer/elwig/src/branch/main/CHANGELOG.md");