Update dependency markdown-it to v14

Author: renovate[bot]

package.json

@@ -25,7 +25,7 @@
   },
   "homepage": "https://github.com/adapttive/markdown-it-external-preview#readme",
   "devDependencies": {
-    "markdown-it": "^12.0.3"
+    "markdown-it": "^14.0.0"
   },
   "dependencies": {
     "browser-or-node": "^1.3.0",