Adding dark mode.

www/main.css

@@ -1,3 +1,18 @@
+@media (prefers-color-scheme: dark) {
+  body {
+    color:#AAA;
+    background-color:#333;
+  }
+}
+
+@media (prefers-color-scheme: light) {
+  body {
+    color:#444;
+    background-color:unset;
+  }
+}
+
+
 body {
   margin:40px auto;
   max-width:800px;