refactor(demos): udpate app background color

Author: simeonoff

src/styles/igniteui-theme.scss

@@ -9,7 +9,7 @@
 $palette: $dark-indigo-palette;
 $schema: $dark-indigo-schema;
 
-$igx-background-color: igx-color($palette, 'surface');
+$igx-background-color: darken(igx-color($palette, 'surface'), 5%);
 $igx-foreground-color: igx-color($palette, 'grays', 900);
 
 body {
@@ -20,6 +20,15 @@ body {
 @include igx-core($direction: ltr);
 @include igx-theme($palette: $palette, $schema: $schema);
 
+@include igx-typography(
+    $font-family: "'Nunito Sans', sans-serif",
+    $type-scale: $indigo-type-scale
+);
+
+@include igx-card-typography($indigo-type-scale, $categories: (
+    title: 'h5',
+));
+
 .nav-header {
     @if luminance($igx-background-color) < .5 {
         @include nav-logo('../assets/images/rsrcs/igniteui-logo-dark-bg', $igx-background-color);