fix(deps): update dependency ejs to v3 [security]

Author: renovate[bot]

package.json

@@ -10,7 +10,7 @@
     "test": "jest && standard"
   },
   "dependencies": {
-    "ejs": "^2.5.7",
+    "ejs": "^3.1.10",
     "jsdom": "^11.3.0",
     "probot": "^6.0.0",
     "probot-attachments": "github:probot/attachments",