doc: fix ESM hook mistypes and links to types

Prior to this commit, the custom loader hooks were:

• missing the Node.js API ref docs types
• missing the function signature from their sections
• linking directly to the specification (not customary)
• had an inconsistent non-nullable JSDoc promise return
• had JSDoc object properties that weren't alpha-sorted
• designated set of non-nullable types when single was fine

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines