fix: add index.scss to npm files (#9385)

Author: joshblack

packages/colors/package.json

@@ -15,7 +15,8 @@
     "es",
     "lib",
     "scss",
-    "umd"
+    "umd",
+    "index.scss"
   ],
   "keywords": [
     "eyeglass-module",

packages/grid/package.json

@@ -11,7 +11,8 @@
   "bugs": "https://github.com/carbon-design-system/carbon/issues",
   "files": [
     "css",
-    "scss"
+    "scss",
+    "index.scss"
   ],
   "keywords": [
     "eyeglass-module",

packages/type/package.json

@@ -16,7 +16,8 @@
     "lib",
     "scss",
     "src",
-    "umd"
+    "umd",
+    "index.scss"
   ],
   "keywords": [
     "eyeglass-module",