Added updated date in schema

schemas/0.1/example.json

@@ -3,6 +3,7 @@
   "id": "https://retribute.me/@Alice.json",
   "url": "https://retribute.me/@Alice.html",
   "title": "Caring is loving",
+  "updated": "2019-05-24T18:56:12.269457",
   "summary": "My name is Alice, I produce Creative Commons electro music. I need your support to continue working on my audio pieces!",
   "identities": [
     {

schemas/0.1/schema.json

@@ -24,6 +24,13 @@
         "https://retribute.me/@Alice.json"
       ]
     },
+    "updated": {
+      "description": "Date of the last update of the profile",
+      "type": "string",
+      "examples": [
+        "2019-05-24T18:57:27.224105"
+      ]
+    },
     "url": {
       "description": "URL of an alternative HTML representation of the retribute profile",
       "type": "string",