added Holopin, closes #1599

Credits @utpalsavliya

sherlock/resources/data.json

@@ -2507,14 +2507,25 @@
     "regexCheck": "[a-z0-9]{4,16}",
     "url": "https://www.dealabs.com/profile/{}",
     "urlMain": "https://www.dealabs.com/",
-    "username_claimed": "blue",
-    "username_unclaimed": "noonewouldeverusethis7"
+    "username_claimed": "blue"
   },
   "wykop.pl": {
     "errorType": "status_code",
     "regexCheck": "[a-z0-9-_]{4,35}",
     "url": "https://www.wykop.pl/ludzie/{}",
     "urlMain": "https://wykop.pl",
-    "username_claimed": "janusz-nowak",
+    "username_claimed": "janusz-nowak"
+  },
+  "Holopin": {
+    "errorMsg": "true",
+    "errorType": "message",
+    "url": "https://holopin.io/@{}",
+    "urlMain": "https://holopin.io",
+    "urlProbe": "https://www.holopin.io/api/auth/username",
+    "request_method": "POST",
+    "request_payload": {
+      "username": "{}"
+    },
+    "username_claimed": "red"
   }
 }