Add option to connect to running chrome process

[wioux]

This branch allows chrome-headless-render-pdf to connect to an already running Chrome process. It adds two new options remoteHost and remotePort, and corresponding CLI options --remote-host and --remote-port. This would be a useful capability so that we can run our browser processes in a separate environment from the rest of our applications.

[Szpadel]

please also update index.d.ts but generally lgtm