Fix grammatical and spelling errors on `npm.md`

[ran-dall]

This PR fixes the essential grammatical and spelling errors in npm.md; however, nothing that should change the meaning of anything.

Please @laurentsimon and @jeffmendoza take a look and review, when convenient.

[ran-dall]

It's also worth noting that the line breaks currently in the document cause breaking errors when opening the document on VSCode. Although it's not required, it might still be worth it to format the document with something like Markdownlint to ensure compatibility across markdown tools.

[laurentsimon]

@olivekl can you take a look?

[jeffmendoza]

@ran-dall We are ready to release, and with the wording/grammar changes in this one, let's go ahead and do this as a follow up to the 1.0 release.

Outlined in the process.md we have "Minor: The fix is obvious or clear. Does not need in-depth review and RFC period. (e.g., typo)". I imagine we will get a number of these with the hopeful attention of the release, and we will work quickly to do a 1.1 release with all the updates that don't change the meaning of the guide.

Oh, and +1 to a linter, I like line limits =) I'll take a look

[ran-dall]

@jeffmendoza I did update this PR to reflect the changes. I also bumped this to Version 1.1 cause we're calling this a minor edit.

[olivekl]

@olivekl can you take a look?

Changes all LGTM. One minor nit: "terrible idea" in line 535 --- rather than a subjective judgement, you could state it in terms of a recommendation. "...but we strongly recommend against this in every situation" or "we strongly recommend that you never do this, since...." or similar strong wording.

[ljharb]

It seems like an objective judgement to me.