docs: auto-generate npm usage for each command

[manekinekko]

Auto-generate npm usage for each command.

NOTE:
These files seem to lack usage description:

• lib/commands/adduser
• lib/commands/bin
• lib/commands/ci
• lib/commands/completion
• lib/commands/dedupe
• lib/commands/doctor
• lib/commands/find-dupes
• lib/commands/install-ci-test
• lib/commands/logout
• lib/commands/ping
• lib/commands/root
• lib/commands/shrinkwrap
• lib/commands/whoami

Edit:
We now generate default usage information for commands with no usage descriptions.

References

Closes #4189

[wraithgar]

The base command file has this snippet for when there is no usage

    if (!this.constructor.usage) {
      usage = `${usage}npm ${this.constructor.name}`
    } else {

[wraithgar]

This is great! I think if we fix the commands with no usage defined, and npx, this is good to go. I'll ask some other cli folks in case they have thoughts.

[wraithgar]

This PR is reminding me we need to clean those html comments out of the man output so here's that PR #4457

[wraithgar]

This is great. I think all we need now is one more special case for npx so that it says npx instead of npm exec and this is good to go!

My previous requested changes have been resolved, but I'm removing this review since there is still one more change requested.

[manekinekko]

Good catch. Fixing this asap!

[wraithgar]

Oops, looks like it changed the npm exec usage to show npx and cleared out the usage on npx.md

[wraithgar]

I didn't even notice it at first but you ALSO fixed the config descriptions to use defaultDescription which they didn't appear to be doing before.

This is GREAT!!!

[manekinekko]

Thank y'all for your prompt responses 💖