build(deps-dev): bump vue-loader from 15.9.3 to 15.9.8

Bumps [vue-loader](https://github.com/vuejs/vue-loader) from 15.9.3 to 15.9.8.
- [Release notes](https://github.com/vuejs/vue-loader/releases)
- [Changelog](https://github.com/vuejs/vue-loader/blob/master/CHANGELOG.md)
- [Commits](vuejs/vue-loader@v15.9.3...v15.9.8)

---
updated-dependencies:
- dependency-name: vue-loader
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

package.json

@@ -94,7 +94,7 @@
     "stylelint-scss": "^3.18.0",
     "stylelint-webpack-plugin": "^2.1.1",
     "url-loader": "^4.1.0",
-    "vue-loader": "^15.9.3",
+    "vue-loader": "^15.9.8",
     "vue-template-compiler": "^2.6.12",
     "wait-on": "^5.2.0",
     "webpack": "^4.44.1",