Add package keywords

Author: adamgraham

package.json

@@ -4,6 +4,12 @@
   "displayName": "Zigurous Graphics Utils",
   "description": "The Graphics Utils package provides scripts and utilities for graphics and rendering purposes in Unity projects.",
   "unity": "2019.4",
+  "keywords": [
+    "graphics",
+    "rendering",
+    "scripts",
+    "utilities"
+  ],
   "repository": "https://github.com/zigurous/unity-graphics-utils",
   "publishConfig": {
     "registry": "https://npm.pkg.github.com/@zigurous"