fix(deps): bump nuxt from 2.14.12 to 2.15.4

Bumps [nuxt](https://github.com/nuxt/nuxt.js) from 2.14.12 to 2.15.4.
- [Release notes](https://github.com/nuxt/nuxt.js/releases)
- [Changelog](https://github.com/nuxt/nuxt.js/blob/dev/RELEASE_PLAN.md)
- [Commits](https://github.com/nuxt/nuxt.js/compare/v2.14.12...v2.15.4)

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

package.json

@@ -20,7 +20,7 @@
     "express": "^4.17.1",
     "lodash": "^4.17.20",
     "microsoft-cognitiveservices-speech-sdk": "^1.14.1",
-    "nuxt": "^2.14.6",
+    "nuxt": "^2.15.4",
     "tmp": "^0.2.1",
     "vue-multiselect": "^2.1.6",
     "xmlbuilder": "^15.1.1"