* chore: update relevant Node.js versions from 8 to 10
* chore: remove node6 and node8 folders from puppeteer-firefox ci
* fix: loosen definition for proc.stdio
* fix: update typescript version used in npm run test-types
Node.js v6 was end-of-life'd in April, 2019, with AWS Lambda prohibiting updaets to the Node.js v6 runtime since June 30, 2019.
This makes it quite safe for us to remove the Node 6 support from the repository.
Cirrus CI got some optimizations for containers based of `microsoft/windowsservercore:latest`.
Now startup time for windows builds is around 1:30 seconds instead of around 4 minutes.
to: @aslushnikov
This patch adds experimental support for Cirrus CI builds.
Cirrus CI has both Windows and Linux, uses google cloud and runs builds
in Docker containers.
This seems to be a promising combination for our needs.
