Update dependency hexo-theme-next to v8.20.0 (#124)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

package.json

@@ -35,7 +35,7 @@
     "hexo-renderer-stylus": "3.0.1",
     "hexo-server": "3.0.0",
     "hexo-tag-embed": "1.0.0",
-    "hexo-theme-next": "8.19.2"
+    "hexo-theme-next": "8.20.0"
   },
   "devDependencies": {
     "markdownlint-cli": "0.40.0"