Add OLED Black map theme

www/settings.js

@@ -20,6 +20,11 @@ var SETTINGS = {
             url: "https://maps.netsyms.net/styles/fiord-color/{z}/{x}/{y}.png",
             name: "Dark Fiord",
             bgcolor: "#45516E"
+        },
+        oledblack: {
+            url: "https://maps.netsyms.net/styles/oled-black/{z}/{x}/{y}.png",
+            name: "OLED Black",
+            bgcolor: "#000000"
         }
     },
     alertsounds: {