pnpm run build should only run turbo build

We apply `--filter` flags to the `pnpm build` command when running in
CI. By introducing the second script via `&&` the filters aren't applied
correctly.

Using a `postbuild` should hopefully fix that.

package.json

@@ -34,7 +34,8 @@
   "scripts": {
     "format": "prettier --write .",
     "lint": "prettier --check . && turbo lint",
-    "build": "turbo build --filter=!./playgrounds/* && node ./scripts/pack-packages.mjs",
+    "build": "turbo build --filter=!./playgrounds/*",
+    "postbuild": "node ./scripts/pack-packages.mjs",
     "dev": "turbo dev --filter=!./playgrounds/*",
     "test": "cargo test && vitest run",
     "test:integrations": "vitest --root=./integrations --no-file-parallelism",