fix: add missing test devDependencies (vitest, @testing-library/*)

The test script runs vitest and imports from @testing-library/react and
@testing-library/jest-dom, but none of these were listed as devDependencies.
Adds vitest ^3.0.5 and all required @testing-library packages matching other
plugin repos in the org.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package-lock.json

@@ -9,7 +9,15 @@
       "version": "0.1.0",
       "license": "Apache-2.0",
       "devDependencies": {
-        "@kinvolk/headlamp-plugin": "^0.13.0"
+        "@kinvolk/headlamp-plugin": "^0.13.0",
+        "@testing-library/jest-dom": "^6.4.8",
+        "@testing-library/react": "^16.0.0",
+        "@testing-library/user-event": "^14.5.2",
+        "jsdom": "^24.0.0",
+        "react": "^18.3.1",
+        "react-dom": "^18.3.1",
+        "react-router-dom": "^5.3.0",
+        "vitest": "^3.0.5"
       }
     },
     "node_modules/@adobe/css-tools": {