feat(uptime): add robots.txt rejection as an uptime check result

Author: klochek

schemas/uptime-results.v1.schema.json

@@ -7,7 +7,12 @@
       "title": "check_status",
       "description": "The status of the check",
       "type": "string",
-      "enum": ["success", "failure", "missed_window"]
+      "enum": [
+        "success",
+        "failure",
+        "missed_window",
+        "disallowed_by_robots"
+      ]
     },
     "CheckStatusReasonType": {
       "title": "check_status_reason_type",