Run npm audit fix

The code is not really run on the website. It is run locally, whenever
the Markdown-formatted files change, to generate the static web pages.

Nevertheless, we can easily quieten the security alerts. So lets' do
precisely that.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

package-lock.json

@@ -26,7 +26,7 @@
     "grunt-contrib-connect": "^3.0.0",
     "grunt-contrib-cssmin": "^4.0.0",
     "grunt-contrib-uglify": "^5.0.1",
-    "grunt-md2html": "^0.5.1"
+    "grunt-md2html": "^0.6.1"
   },
   "engines": {
     "node": ">=0.8.0"