Add commander dependency

We use this explicitly in the following scripts:

- scripts/merge-i18n-files.ts
- scripts/sync-i18n-files.ts

Previously it was assumed that `commander` was available in the en-
vironment, which seems to have been provided by cypress.

Author: alanorth

package-lock.json

@@ -191,6 +191,7 @@
     "@typescript-eslint/rule-tester": "^7.18.0",
     "@typescript-eslint/utils": "^7.18.0",
     "axe-core": "^4.10.2",
+    "commander": "^14.0.1",
     "compression-webpack-plugin": "^9.2.0",
     "copy-webpack-plugin": "^6.4.1",
     "cross-env": "^7.0.3",