chore(deps-dev): bump gulp from 3.9.1 to 4.0.0 (#137)

Bumps [gulp](https://github.com/gulpjs/gulp) from 3.9.1 to 4.0.0.
- [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...v4.0.0)

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

package.json

@@ -176,7 +176,7 @@
 	"devDependencies": {
 		"@types/node": "^10.12.12",
 		"fs-nextra": "^0.3.7",
-		"gulp": "^3.9.1",
+		"gulp": "^4.0.0",
 		"gulp-sourcemaps": "^2.6.4",
 		"gulp-typescript": "^5.0.0",
 		"merge2": "^1.2.3",