feat: upgrade hast-util-to-string from 2.0.0 to 3.0.0

Snyk has created this PR to upgrade hast-util-to-string from 2.0.0 to 3.0.0.

See this package in npm:
https://www.npmjs.com/package/hast-util-to-string

See this project in Snyk:
https://app.snyk.io/org/thetutlage/project/f6d15bcb-fe7b-443c-ae08-f1c5db7feb80?utm_source=github&utm_medium=referral&page=upgrade-pr

package.json

@@ -66,7 +66,7 @@
   "dependencies": {
     "front-matter": "^4.0.2",
     "hast-util-to-html": "^8.0.4",
-    "hast-util-to-string": "^2.0.0",
+    "hast-util-to-string": "^3.0.0",
     "hastscript": "^8.0.0",
     "mdast-util-to-hast": "^12.3.0",
     "mdast-util-toc": "^6.1.1",