Add package documentation and changelog urls

Author: adamgraham

package.json

@@ -10,6 +10,8 @@
     "scripts"
   ],
   "repository": "https://github.com/zigurous/unity-animation-library",
+  "documentationUrl": "https://docs.zigurous.com/com.zigurous.animation/",
+  "changelogUrl": "https://docs.zigurous.com/com.zigurous.animation/changelog/CHANGELOG.html",
   "publishConfig": {
     "registry": "https://npm.pkg.github.com/@zigurous"
   },