build(deps): bump showdown from 1.9.1 to 2.1.0 (#284)

Bumps [showdown](https://github.com/showdownjs/showdown) from 1.9.1 to 2.1.0.
- [Release notes](https://github.com/showdownjs/showdown/releases)
- [Changelog](https://github.com/showdownjs/showdown/blob/master/CHANGELOG.md)
- [Commits](https://github.com/showdownjs/showdown/compare/1.9.1...2.1.0)

---
updated-dependencies:
- dependency-name: showdown
  dependency-version: 2.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -6,6 +6,6 @@
     "@actions/core": "^3.0.0",
     "@actions/glob": "^0.6.1",
     "nodemailer": "^8.0.5",
-    "showdown": "^1.9.1"
+    "showdown": "^2.1.0"
   }
 }