add documentation url to package

Author: András Kurai

UnityResourceGenerator/Assets/AutSoft.UnityResourceGenerator/package.json

@@ -5,6 +5,7 @@
     "description": "Generate path strings for Resources.Load",
     "license": "MIT",
     "changelogUrl": "https://github.com/AutSoft/UnityResourceGenerator/blob/main/CHANGELOG.md",
+    "documentationUrl": "https://autsoft.github.io/UnityResourceGenerator/",
     "unity": "2019.4",
     "keywords": [
         "Editor",