Bump minimist and mkdirp

Bumps [minimist](https://github.com/minimistjs/minimist), [minimist](https://github.com/minimistjs/minimist) and [mkdirp](https://github.com/isaacs/node-mkdirp). These dependencies needed to be updated together.

Updates `minimist` from 1.2.5 to 1.2.8
- [Release notes](https://github.com/minimistjs/minimist/releases)
- [Changelog](https://github.com/minimistjs/minimist/blob/main/CHANGELOG.md)
- [Commits](https://github.com/minimistjs/minimist/compare/v1.2.5...v1.2.8)

Updates `minimist` from 1.2.0 to 1.2.8
- [Release notes](https://github.com/minimistjs/minimist/releases)
- [Changelog](https://github.com/minimistjs/minimist/blob/main/CHANGELOG.md)
- [Commits](https://github.com/minimistjs/minimist/compare/v1.2.5...v1.2.8)

Updates `mkdirp` from 0.5.1 to 0.5.5
- [Release notes](https://github.com/isaacs/node-mkdirp/releases)
- [Changelog](https://github.com/isaacs/node-mkdirp/blob/main/CHANGELOG.md)
- [Commits](https://github.com/isaacs/node-mkdirp/compare/0.5.1...v0.5.5)

---
updated-dependencies:
- dependency-name: minimist
  dependency-type: indirect
- dependency-name: minimist
  dependency-type: indirect
- dependency-name: mkdirp
  dependency-type: indirect
...

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

package.json

@@ -16,7 +16,7 @@
     "prismjs": "^1.23.0",
     "redis": "^3.0.2",
     "rss": "^1.2.2",
-    "showdown": "^2.0.2"
+    "showdown": "^1.9.1"
   },
   "devDependencies": {
     "coveralls": "^3.0.4",