Update dependency nyc to v15 (#20)

* Update document site

* Update dependency nyc to v15

Co-authored-by: yosuke ota <[email protected]>
Co-authored-by: Renovate Bot <[email protected]>

Author: 3 people

package.json

@@ -31,7 +31,7 @@
     "globals": "^13.0.0",
     "mocha": "^9.0.0",
     "npm-run-all": "^4.1.5",
-    "nyc": "^14.1.1",
+    "nyc": "^15.0.0",
     "opener": "^1.5.1",
     "rimraf": "^3.0.0",
     "semver": "^6.3.0",