Bump hexo-generator-index from 3.0.0 to 4.0.0

Bumps [hexo-generator-index](https://github.com/hexojs/hexo-generator-index) from 3.0.0 to 4.0.0.
- [Release notes](https://github.com/hexojs/hexo-generator-index/releases)
- [Commits](hexojs/hexo-generator-index@v3.0.0...v4.0.0)

---
updated-dependencies:
- dependency-name: hexo-generator-index
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

package.json

@@ -15,7 +15,7 @@
     "hexo": "^7.1.1",
     "hexo-generator-archive": "^2.0.0",
     "hexo-generator-category": "^2.0.0",
-    "hexo-generator-index": "^3.0.0",
+    "hexo-generator-index": "^4.0.0",
     "hexo-generator-sitemap": "^3.0.1",
     "hexo-generator-tag": "^2.0.0",
     "hexo-renderer-ejs": "^2.0.0",