add heroku-self-ping

Author: Amoki

Diff for: package.json

@@ -33,7 +33,7 @@
   "dependencies": {
     "anyfetch-hydrater": "^2.2.0",
     "async": "0.9.x",
-    "heroku-self-ping": "~1.1.1",
+    "heroku-self-ping": "^1.1.2",
     "html-entities": "^1.1.2"
   },
   "devDependencies": {