Add toast component documentation

- Add documentation that describes when and how to use a toast message
with code snippets
- Add an informational toast method in the BVToastMixin
- Add BVToastMixin to enhaceApp to register mixin globally.

Signed-off-by: Derick Montague <derick.montague@ibm.com>
Change-Id: I89bf2aa8b3fdb9294354a80c98ccf692b6e3615a
diff --git a/src/locales/en-US.json b/src/locales/en-US.json
index 0bf4051..1e676ee 100644
--- a/src/locales/en-US.json
+++ b/src/locales/en-US.json
@@ -28,7 +28,8 @@
       "off": "Off",
       "on": "On",
       "success": "Success",
-      "warning": "Warning"
+      "warning": "Warning",
+      "informational": "Informational"
     }
   },
   "appHeader": {