fix: scss deprecation warnings and wrong example name (#462)

* Fixes a couple of deprecation warnings from Sass due to .scss files importing .css, which will start breaking at some point.
* Fixes one of the examples not loading due to it not being renamed after it was changed in the Material repo.

Author: crisbeto

material.angular.io/angular.json

@@ -32,7 +32,7 @@
                 "input": "src/main.scss"
               },
               {
-                "input": "src/highlightjs/material-light.css"
+                "input": "src/highlightjs/material-light.scss"
               },
               {
                 "input": "src/assets/pink-bluegrey.css",
@@ -108,7 +108,7 @@
                 "input": "src/main.scss"
               },
               {
-                "input": "src/highlightjs/material-light.css"
+                "input": "src/highlightjs/material-light.scss"
               },
               {
                 "input": "src/assets/pink-bluegrey.css",