Bump minimatch and gulp in /website

Bumps [minimatch](https://github.com/isaacs/minimatch) to 3.1.2 and updates ancestor dependency [gulp](https://github.com/gulpjs/gulp). These dependencies need to be updated together.


Updates `minimatch` from 2.0.10 to 3.1.2
- [Release notes](https://github.com/isaacs/minimatch/releases)
- [Commits](https://github.com/isaacs/minimatch/compare/v2.0.10...v3.1.2)

Updates `gulp` from 3.9.1 to 4.0.2
- [Release notes](https://github.com/gulpjs/gulp/releases)
- [Changelog](https://github.com/gulpjs/gulp/blob/master/CHANGELOG.md)
- [Commits](https://github.com/gulpjs/gulp/compare/v3.9.1...v4.0.2)

---
updated-dependencies:
- dependency-name: minimatch
  dependency-type: indirect
- dependency-name: gulp
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

website/package.json

@@ -2,7 +2,7 @@
   "dependencies": {
     "codemirror": "^5.37.0",
     "critical": "^1.3.2",
-    "gulp": "^3.9.1",
+    "gulp": "^4.0.2",
     "gulp-rename": "^1.2.3",
     "html5shiv": "^3.7.3",
     "jquery": "^3.3.1",