fix(Worker): Add missing dep for Puppeteer
fix(Worker): Add missing dep for Puppeteer

Closes #987.

Because we are using the `pipe: true` option in Encoda, the real Puppeteer errors can be obscured. To test, try to launch Puppeteer in the container without that option:

```sh
docker run -it stencila/hub-worker node -e "require('puppeteer').launch({'args': ['--no-sandbox']}).then(browser => browser.close())"
```

stencila/hub,stencila/hub,stencila/hub,stencila/hub,stencila/hub