add jest as extension devDep, go back to using makefile foreach syntax

Signed-off-by: Sebastian Malton <sebastian@malton.name>

extensions/license-menu-item/package.json

@@ -10,8 +10,9 @@
   },
   "dependencies": {},
   "devDependencies": {
-    "@types/webpack": "^4.41.17",
     "@k8slens/extensions": "file:../../src/extensions/npm/extensions",
+    "@types/webpack": "^4.41.17",
+    "jest": "^26.6.3",
     "mobx": "^5.15.5",
     "react": "^16.13.1",
     "ts-loader": "^8.0.4",