Add alert message component and documentation

- Add custom alert component to simplify the use of custom alerts
- Add documentation for using the custom alert
- Update the login error alert to use the alert component instead of
the Bootstrap-vue component.
- Register alert component in enhanceApp
- Replace Sass variables used in the StatusIcon component style block
to use the Boostrap theme-color and gray Sass functions so the colors
can be used in the Vuepress documentation custom components

Signed-off-by: Derick Montague <derick.montague@ibm.com>
Change-Id: Ibd93402c919a42bd5c24cc9e7c6c8fc6f17a4db4
diff --git a/src/components/Global/StatusIcon.vue b/src/components/Global/StatusIcon.vue
index 96074ee..1114321 100644
--- a/src/components/Global/StatusIcon.vue
+++ b/src/components/Global/StatusIcon.vue
@@ -33,20 +33,20 @@
 .status-icon {
   vertical-align: text-bottom;
   &.success {
-    fill: $success;
+    fill: theme-color('success');
   }
   &.danger {
-    fill: $danger;
+    fill: theme-color('danger');
   }
   &.secondary {
-    fill: $gray-600;
+    fill: gray('600');
 
     svg {
       transform: rotate(-45deg);
     }
   }
   &.warning {
-    fill: $warning;
+    fill: theme-color('warning');
   }
 }
 </style>