improve index.html interface with ninja template

site/assets/fonts/material-design/scss/_functions.scss

@@ -0,0 +1,16 @@
+@function char($character-code) {
+    @if function-exists("selector-append") {
+        @return unquote("\"\\#{$character-code}\"");
+    }
+
+    @if "\\#{'x'}" == "\\x" {
+        @return str-slice("\x", 1, 1) + $character-code;
+    }
+    @else {
+        @return #{"\"\\"}#{$character-code + "\""};
+    }
+}
+
+@function mdi($name) {
+    @return char(map-get($mdi-icons, $name));
+}