fix: patch 8 of 9 npm vulnerabilities via pnpm.overrides

Move vulnerability overrides from npm-format top-level `overrides` to
pnpm-format `pnpm.overrides`. Add flatted override to patch the
high-severity prototype pollution CVE. All 5 high + 3 moderate severity
issues are now resolved.

Remaining: elliptic (low, no patch available upstream).

Co-Authored-By: Paperclip <noreply@paperclip.ing>

package.json

@@ -30,9 +30,12 @@
     "react": "^18.0.0",
     "react-dom": "^18.0.0"
   },
-  "overrides": {
-    "tar": "^7.5.11",
-    "undici": "^7.24.3"
+  "pnpm": {
+    "overrides": {
+      "tar": "^7.5.11",
+      "undici": "^7.24.3",
+      "flatted": "^3.4.2"
+    }
   },
   "devDependencies": {
     "@kinvolk/headlamp-plugin": "^0.13.0",