Bump markdown-it from 10.0.0 to 12.3.2

Bumps [markdown-it](https://github.com/markdown-it/markdown-it) from 10.0.0 to 12.3.2.
- [Release notes](https://github.com/markdown-it/markdown-it/releases)
- [Changelog](https://github.com/markdown-it/markdown-it/blob/master/CHANGELOG.md)
- [Commits](markdown-it/markdown-it@10.0.0...12.3.2)

---
updated-dependencies:
- dependency-name: markdown-it
  dependency-type: direct:production
...

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

Author: dependabot[bot]

package-lock.json

@@ -10,7 +10,7 @@
   "dependencies": {
     "disqus-react": "^1.0.8",
     "firebase": "^7.14.1",
-    "markdown-it": "^10.0.0",
+    "markdown-it": "^12.3.2",
     "mdc-react": "^0.14.6",
     "react": "^16.13.1",
     "react-dom": "^16.13.1",