fix(deps): add bluebird as an actual dep

Author: zkat

package.json

@@ -29,6 +29,7 @@
   },
   "license": "ISC",
   "dependencies": {
+    "bluebird": "^3.5.1",
     "lru-cache": "^4.1.2",
     "make-fetch-happen": "^3.0.0",
     "npm-package-arg": "^6.0.0",