build(deps-dev): bump nyc from 14.1.1 to 15.1.0

Bumps [nyc](https://github.com/istanbuljs/nyc) from 14.1.1 to 15.1.0.
- [Release notes](https://github.com/istanbuljs/nyc/releases)
- [Changelog](https://github.com/istanbuljs/nyc/blob/master/CHANGELOG.md)
- [Commits](https://github.com/istanbuljs/nyc/compare/v14.1.1...v15.1.0)

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

package.json

@@ -77,7 +77,7 @@
     "jszip": "^3.1.5",
     "mocha": "^5.2.0",
     "mocha-webpack": "^1.0.1",
-    "nyc": "^14.1.1",
+    "nyc": "^15.1.0",
     "pre-commit": "^1.2.2",
     "prettier": "^1.15.2",
     "prompt": "^1.0.0",