fix: upgrade markdown-it-anchor from 8.1.2 to 8.6.7

Snyk has created this PR to upgrade markdown-it-anchor from 8.1.2 to 8.6.7.

See this package in npm:
https://www.npmjs.com/package/markdown-it-anchor

See this project in Snyk:
https://app.snyk.io/org/nexuscompute/project/b621f8be-de26-4791-bbe0-28c6fc5bd7f5?utm_source=github&utm_medium=referral&page=upgrade-pr

package.json

@@ -77,7 +77,7 @@
     "lit-html": "^1.3.0",
     "lodash.get": "^4.4.2",
     "markdown-it": "12.0.1",
-    "markdown-it-anchor": "8.1.2",
+    "markdown-it-anchor": "8.6.7",
     "markdown-it-attrs": "^4.1.4",
     "markdown-it-deflist": "^2.1.0",
     "ms": "^2.1.3",