chore(deps): bump log4js from 3.0.6 to 6.4.0

Bumps [log4js](https://github.com/log4js-node/log4js-node) from 3.0.6 to 6.4.0.
- [Release notes](https://github.com/log4js-node/log4js-node/releases)
- [Changelog](https://github.com/log4js-node/log4js-node/blob/master/CHANGELOG.md)
- [Commits](https://github.com/log4js-node/log4js-node/compare/v3.0.6...v6.4.0)

---
updated-dependencies:
- dependency-name: log4js
  dependency-type: direct:production
...

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

package.json

@@ -16,7 +16,7 @@
   "dependencies": {
     "chart.js": "^2.7.3",
     "highlight.js": "^9.13.0",
-    "log4js": "^3.0.6",
+    "log4js": "^6.4.0",
     "markdown-it": "^9.0.1",
     "markdown-it-anchor": "^5.2.4",
     "markdown-it-emoji": "^1.4.0",