fix: android build for npm installs

- Move `ZstdPackage.kt` to `com.reactnativezstd`
  to match Android namespace, fixing autolinking
- Add `externals/zstd/build/cmake` and
  `lib/libzstd.pc.in` to `files` for npm builds
- Set white background in example app

Author: Andarius

.github/workflows/ci.yml

@@ -146,7 +146,6 @@ jobs:
         uses: actions/setup-node@395ad3262231945c25e8478fd5baf05154b1d79f # v6.1.0
         with:
           node-version: 22
-          registry-url: https://registry.npmjs.org
 
       - name: Restore node_modules
         uses: actions/cache/restore@9255dc7a253b0ccc959486e2bca901246202afeb # v5.0.1
@@ -156,6 +155,9 @@ jobs:
             example/node_modules
           key: node-modules-${{ hashFiles('yarn.lock') }}
 
+      - name: Upgrade npm for OIDC trusted publishing
+        run: npm install -g npm@latest
+
       - name: Configure git
         run: |
           git config --global user.email "julien.brayere@obitrain.com"