readme: add `PUPPETEER_SKIP_CHROMIUM_DOWNLOAD` note (#671)
readme: add `PUPPETEER_SKIP_CHROMIUM_DOWNLOAD` note (#671)


brutalcrozt/puppeteer,elisherer/puppeteer,ianchn/puppeteer,elisherer/puppeteer,puppeteer/puppeteer,ianchn/puppeteer,a1ph/puppeteer,puppeteer/puppeteer,GoogleChrome/puppeteer,puppeteer/puppeteer,puppeteer/puppeteer,GoogleChrome/puppeteer,GoogleChrome/puppeteer,michaelfward/puppeteer,a1ph/puppeteer,brutalcrozt/puppeteer,michaelfward/puppeteer