feat: support node 16

[ewanharris]

This adds support for Node.js 16, I also tested the changes made against 12.13.0, 12.22.0, and 14.6.1.

In summary:

• Bump to latest node-pre-gyp
• Remove setting of c++11 stdlib due to V8/Node.js now requiring c++14
• Updates the usage of AtExit due to compile error on 16
  • This has been a warning since 13.5.0/12.15.0 it appears, and the API has supported 3 arguments since 8.0.0. The version check could potentially be removed in favour of always calling with 3 args
  • As stated in that PR, using AddEnvironmentCleanupHook is preferred, but I figured it was best to stick with whats there already

[cb1kenobi]

Tested and looks good! APPROVED!