[cna] For pnpm ignore postinstall from `sharp` and `unrs-resolver` (#83168)
Fixes: https://github.com/vercel/next.js/issues/83158
There's still two other postinstall that are ignored if you use tw and
eslint's next config (?):
```
╭ Warning ───────────────────────────────────────────────────────────────────────────────────╮
│ │
│ Ignored build scripts: @tailwindcss/oxide, unrs-resolver. │
│ Run "pnpm approve-builds" to pick which dependencies should be allowed to run scripts. │
│ │
╰────────────────────────────────────────────────────────────────────────────────────────────╯
```
---------
Co-authored-by: Sebastian Sebbie Silbermann <sebastian.silbermann@vercel.com>