chore(deps): update dependency remark-slug to v6 (#5064)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

www/package.json

@@ -45,7 +45,7 @@
     "react-docgen": "^5.3.0",
     "react-dom": "^16.13.1",
     "react-live": "^2.2.2",
-    "remark-slug": "^5.1.2",
+    "remark-slug": "^6.0.0",
     "shakespeare-data": "^3.0.0",
     "yup": "^0.28.3"
   },