Proposal: make require of puppeteer effectful

[mikesol]

The require of puppeteer via var puppeteer = require("puppeteer"); crashes when the puppeteer library is not used (ie when using packages like chrome-aws-lambda). If the require of puppeteer is effectful and puppeteer is passed to launch, or alternatively if puppeteer is not exposed and is just required on the fly in launch, then that will prevent the crash.