Add ncu-env-check

[bnb]

There's a pretty decent number of requirements to contribute to node that are easy to fumble. It would be lovely if node-core-utils provided a suite of checks that can be run with a single command (ncu-env-check) to validate that a given environment is properly configured.

Here's the list I have so far for Linux:

• system has git
• system has python3
• system has g++
• system has make
• origin is set to something that's not git@github.com:nodejs/node.git (and potentially check if it's a fork of nodejs/node for even better DX, which could be checked via the API (thanks @zkatfor the tip <3))
• upstream is set to git@github.com:nodejs/node.git
• check that git config user.name is set
• check that git config user.email is set
• check that an SSH key matching one published to GitHub is set

I'm sure there's a number of others that could be added, too.

This would be particularly useful if we are to follow through on nodejs/node#39672, particularly for getting people up and running with minimal friction.