[DEV/DEP]: Bump terser from 5.18.2 to 5.21.0

Bumps [terser](https://github.com/terser/terser) from 5.18.2 to 5.21.0.
- [Changelog](https://github.com/terser/terser/blob/master/CHANGELOG.md)
- [Commits](terser/terser@v5.18.2...v5.21.0)

---
updated-dependencies:
- dependency-name: terser
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

package.json

@@ -37,7 +37,7 @@
         "mocha": "~10.2.0",
         "nyc": "^15.1.0",
         "puppeteer": "~20.7.2",
-        "terser": "~5.18.1",
+        "terser": "~5.21.0",
         "vue-tabs-component": "^1.5.0",
         "vuepress": "^1.9.7",
         "vuepress-plugin-tabs": "^0.3.0",