GH Actions: use npm ci instead of npm update

It is generally recommended to use `npm ci` in CI, see for example:

- https://docs.npmjs.com/cli/v10/commands/npm-ci#description
- https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-nodejs#example-using-npm
- https://support.deploybot.com/article/131-why-developers-should-use-npm-ci-instead-of-npm-install-and-its-benefits

.github/workflows/main.yml

@@ -16,7 +16,7 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version: '16'
-      - run: npm install
+      - run: npm ci
       - name: Use stable versions of KSC and JS runtime
         run: |
           npm install kaitai-struct-compiler@latest kaitai-struct@latest