Bump serialize-javascript in /chapter-8/angular-example

Bumps [serialize-javascript](https://github.com/yahoo/serialize-javascript) from 2.1.2 to 3.1.0.
- [Release notes](https://github.com/yahoo/serialize-javascript/releases)
- [Commits](yahoo/serialize-javascript@v2.1.2...v3.1.0)

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

Author: dependabot[bot]

chapter-8/angular-example/package-lock.json

@@ -21,7 +21,7 @@
     "@angular/router": "~7.2.0",
     "core-js": "^2.5.4",
     "rxjs": "~6.3.3",
-    "serialize-javascript": "^2.1.2",
+    "serialize-javascript": "^3.1.0",
     "tslib": "^1.9.0",
     "zone.js": "~0.8.26"
   },