refactor: Bump mailgun.js from 12.8.0 to 13.0.0 (#259)

Author: mtrezza

package-lock.json

@@ -50,7 +50,7 @@
     "jasmine": "6.2.0",
     "jasmine-spec-reporter": "7.0.0",
     "madge": "5.0.1",
-    "mailgun.js": "12.8.0",
+    "mailgun.js": "13.0.0",
     "nyc": "18.0.0",
     "semantic-release": "25.0.3",
     "typescript": "6.0.3"