Bump lodash from 4.17.13 to 4.17.21

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.13 to 4.17.21.
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](lodash/lodash@4.17.13...4.17.21)

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

Author: dependabot[bot]

package-lock.json

@@ -38,7 +38,7 @@
     "gulp-uglifycss": "^1.0.5",
     "gulp-webserver": "^0.9.1",
     "jshint": "^2.9.3",
-    "lodash": "4.17.13",
+    "lodash": "4.17.21",
     "lodash.template": "4.5.0",
     "mocha-jsdom": "^2.0.0",
     "nyc": "^15.0.0",