Switch Bedstead Web page to dark-on-light.

I recently saw Bedstead featured on a collection of programming fonts
and noticed that it was much prettier there than on its own Web page.
That's clearly wrong, and I think displaying it in a light colour on a
dark background (and with less than maximum contrast) helped.  The new
colours are based on my memory of the old Philips green-screen monitor
currently connected to my Beeb (because I'm too lazy to get out of bed
and check it).

bedstead.css

@@ -33,3 +33,16 @@ h1, h2 {
 ul {
     list-style-type: "\2022  ";
 }
+
+/* Colours that make Bedstead look better (imitating my green monitor) */
+body {
+    background-color: #222;
+    color: #8f8;
+}
+
+:link {
+  color: #cfc;
+}
+:visited {
+  color: #bfb;
+}