docs(api.md): add explanation to page.waitForNavigation (#2354)
docs(api.md): add explanation to page.waitForNavigation (#2354)

Fixes #1860

puppeteer/puppeteer,puppeteer/puppeteer,puppeteer/puppeteer,puppeteer/puppeteer,GoogleChrome/puppeteer,GoogleChrome/puppeteer,GoogleChrome/puppeteer