docs: explicit call out for when process.cwd is set

[rhettjay]

Add clarity to docs to resolve #1956.

[wesleytodd]

Glad to see this ended with a docs change. Not sure how much it matters, but even this wording is a bit incorrect in that it is "at the time the class is instantiated" right? For nearly all users I think that should be import time, but I almost feel like this could generate a few questions from folks if they are using the class and passing a cwd. Not sure I have a good suggestion seeing as even on the initial issue report my brain skipped right over the important detail of chdir in the middle of the program but just wanted to point it out.

My low effort idea is to phrase it as current working directory (default: process.cwd() at class instantiation time).

[rhettjay]

I went back and forth on this locally before pushing up. I ended with import because of the PR on standard-engine. You're right though, it'll probably add to the confusion. I wonder if perhaps we opt for yours with a guided hint:
current working directory (default: process.cwd() at class instantiation time -- see standard-engine docs
Thoughts?

[wesleytodd]

Honestly I am not very opinionated, just wanted to share what caught my eye reading it. I like the wording in this last more explicit one, but I agree that if end users wanting to do this understand and use "at import time" more then we should go with that. @regseb any thoughts?

[regseb]

Standard only exports an object with the lintText() and lintFiles() functions. Is there a Node.js API?

This is an instance of the StandardEngine class, but the user doesn't know it. He may think that the Standard code is:

export default {
    "lintText": function (text, opts) {
        // Do something.
        return result;
    },
    "lintFiles": function (files, opts) {
        // Do something.
        return result;
    },
};

I think that with the term "at class instantiation time", the user may be confused: "which class?"

I find the wording "at import time" correct.