add share image to repo and update default og:image

Author: hazel-nut

main/docs.json

@@ -8,7 +8,8 @@
   },
   "seo": {
     "metatags": {
-      "canonical": "https://auth0.com"
+      "canonical": "https://auth0.com",
+      "og:image": "/docs/images/share-image.png"
     }
   },
   "colors": {