docs: add new user to API.md

[Henry-Hong]

Hi 👋

This PR adds picocolors to the list

As you can see, picocolors using API from packagephobia but get Forbidden error because of API block policy.

And don't worry. I set appropriate user-agent header too here.

[vercel]

@Henry-Hong is attempting to deploy a commit to the Package Phobia Team on Vercel.

A member of the Team first needs to authorize it.

[styfle]

Thanks, is this just for a benchmark of picocolors or does it use package phobia at runtime too?

[vercel]

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Name	Status	Preview	Updated (UTC)
packagephobia	✅ Ready (Inspect)	Visit Preview	Aug 3, 2024 1:11am

[Henry-Hong]

Thanks, is this just for a benchmark of picocolors or does it use package phobia at runtime too?

Just for benchmark during CI pipelines. It compares other CLI tools build sizes.