feat(aio): callout, code ex header styles

lighten up code ex background

aio/src/styles/2-modules/_callout.scss

@@ -0,0 +1,47 @@
+.callout {
+  @extend .alert;
+  padding: 0px;
+  border-left: none !important;
+  border-radius: 4px;
+
+  header {
+    color: $white;
+    line-height: 24px;
+    font-weight: 500;
+    text-transform: uppercase;
+    border-radius: 4px 4px 0 0;
+  }
+
+  p {
+    padding: 16px;
+    margin: 0px;
+    font-size: 14px;
+  }
+
+  &.is-critical {
+    border-color: $brightred;
+    background: rgba($brightred, 0.05);
+
+    header {
+      background: $brightred;
+    }
+  }
+
+  &.is-important {
+    border-color: $orange;
+    background: rgba($orange, 0.05);
+
+    header {
+      background: $amber-700;
+    }
+  }
+
+  &.is-helpful {
+    border-color: $blue;
+    background: rgba($blue, 0.05);
+
+    header {
+      background: $blue;
+    }
+  }
+}

aio/src/styles/2-modules/_code.scss

@@ -1,6 +1,6 @@
 code-example,
 code-tabs md-tab-body {
-    background-color: $backgroundgray;
+    background-color: rgba($backgroundgray, 0.2);
     border: 0.5px solid $lightgray;
     border-radius: 5px;
     color: $darkgray;
@@ -20,8 +20,7 @@ code-example.code-shell, code-example[language=sh], code-example[language=bash]
 }
 
 code-example header {
-  background-color: $mediumgray;
-  border: 0.5px solid $mediumgray;
+  background-color: $accentblue;
   border-radius: 5px 5px 0 0;
   color: $offwhite;
   font-size: 16px;

aio/src/styles/2-modules/_modules-dir.scss

@@ -20,4 +20,5 @@
    @import 'api-list';
    @import 'hr';
    @import 'live-example';
-   @import 'scrollbar';
+   @import 'scrollbar';
+   @import 'callout';