[MM-60792] Add support for loading experimental (e.g., in progress) languages (#29009)

* Add support for loading experimental (e.g., in progress) languages

* Fix e2e config

* Improve language labels

* Improvements

webapp/package.json

@@ -16,7 +16,8 @@
     "check": "npm run check --workspaces --if-present",
     "fix": "npm run fix --workspaces --if-present",
     "check-types": "npm run check-types --workspaces --if-present",
-    "clean": "npm run clean --workspaces --if-present"
+    "clean": "npm run clean --workspaces --if-present",
+    "gen-lang-imports": "node scripts/gen_lang_imports.mjs"
   },
   "dependencies": {
     "react-intl": "6.6.2",