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/assets/styles/_obmc-custom.scss b/src/assets/styles/_obmc-custom.scss
index 66cebda..2a8d896 100644
--- a/src/assets/styles/_obmc-custom.scss
+++ b/src/assets/styles/_obmc-custom.scss
@@ -39,6 +39,7 @@
 
 @import "~bootstrap-vue/src/index.scss";
 
+@import "./alerts";
 @import "./buttons";
 @import "./form-components";
 @import "./modal";