Revise NPM to npm

[tekapo]

npm seems to be all lower case.
https://www.npmjs.com/about

[github-actions]

👋 Thanks for your first Pull Request and for helping build the future of Gutenberg and WordPress, @tekapo! In case you missed it, we'd love to have you join us in our Slack community, where we hold regularly weekly meetings open to anyone to coordinate with each other.

If you want to learn more about WordPress development in general, check out the Core Handbook full of helpful information.

[github-actions]

Congratulations on your first merged pull request, @tekapo! We'd like to credit you for your contribution in the post announcing the next WordPress release, but we can't find a WordPress.org profile associated with your GitHub account. When you have a moment, visit the following URL and click "link your GitHub account" under "GitHub Username" to link your accounts:

https://profiles.wordpress.org/me/profile/edit/

And if you don't have a WordPress.org account, you can create one on this page:

https://login.wordpress.org/register

Kudos!