docs: update environment configuration section

[klaemo]

What is the purpose of this pull request? (put an "X" next to item)

[x] Documentation update
[ ] Bug fix
[ ] New feature
[ ] Other, please explain:

What changes did you make? (Give an overview)
I added an example illustrating the standard.env property in package.json.

Which issue (if any) does this pull request address?

Standard's environment configuration syntax in package.json is slightly different to what is documented for ESLint. This changed in version 17 of standard. Before, it accepted the ESLint syntax.

References: #1814

Standard

{
  "standard": {
    "env": ["mocha"]
  }
}

ESLint

{
  "standard": {
    "env": {
      "mocha": true
    }
  }
}

Is there anything you'd like reviewers to focus on?

In all honesty, I think the underlying issue should probably be fixed instead 😅

[welcome]

🙌 Thanks for opening this pull request! You're awesome.

[LinusU]

Neat 👍

[LinusU]

Hmm, actually, I didn't understand that current ESLint versions still uses the object syntax. I thought that the change in Standard was due to upgrading to a newer ESLint version.

I think it would be better if we make sure that the "proper" way works instead 🤔

This probably needs to be done in standard-engine