fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-ANSIREGEX-1583908
- https://snyk.io/vuln/SNYK-JS-DECODEURICOMPONENT-3149970
- https://snyk.io/vuln/SNYK-JS-GLOBPARENT-1016905
- https://snyk.io/vuln/SNYK-JS-INFLIGHT-6095116
- https://snyk.io/vuln/SNYK-JS-INI-1048974
- https://snyk.io/vuln/SNYK-JS-KINDOF-537849
- https://snyk.io/vuln/SNYK-JS-MINIMATCH-3050818
- https://snyk.io/vuln/SNYK-JS-MINIMIST-2429795
- https://snyk.io/vuln/SNYK-JS-MINIMIST-559764
- https://snyk.io/vuln/SNYK-JS-MIXINDEEP-450212
- https://snyk.io/vuln/SNYK-JS-SEMVER-3247795
- https://snyk.io/vuln/SNYK-JS-SETVALUE-1540541
- https://snyk.io/vuln/SNYK-JS-SETVALUE-450213
- https://snyk.io/vuln/SNYK-JS-TAR-1536528
- https://snyk.io/vuln/SNYK-JS-TAR-1536531
- https://snyk.io/vuln/SNYK-JS-TAR-1536758
- https://snyk.io/vuln/SNYK-JS-TAR-1579147
- https://snyk.io/vuln/SNYK-JS-TAR-1579152
- https://snyk.io/vuln/SNYK-JS-TAR-1579155
- https://snyk.io/vuln/SNYK-JS-TAR-174125
- https://snyk.io/vuln/SNYK-JS-TAR-6476909
- https://snyk.io/vuln/SNYK-JS-UNSETVALUE-2400660
- https://snyk.io/vuln/npm:chownr:20180731

package.json

@@ -2,7 +2,7 @@
   "description": "Atom docs",
   "private": true,
   "dependencies": {
-    "gulp": "^4.0.0",
+    "gulp": "^5.0.0",
     "gulp-coffee": "^2.3.1",
     "gulp-concat": "^2.6.0",
     "gulp-connect": "5.5.0",