Fix typos in API.md ('Names links' -> 'Named links', 'unknownMisees' -> 'unknownMisses')

[jeremykohn]

This PR corrects 3 typos in the API docs, as follows:

---

1. link(ref)

"Names links are recommended for most use cases"

-->

"Named links are recommended for most use cases"

---

2. array.includesRequiredBoth

{
    knownMisses: Array<string>, // Labels of all the missing values
    unknownMisees: number // Count of missing values that didn't have a label
}

-->

{
    knownMisses: Array<string>, // Labels of all the missing values
    unknownMisses: number // Count of missing values that didn't have a label
}

---

3. array.includesRequiredUnknowns

{
    unknownMisees: number // Count of missing values that didn't have a label
}

-->

{
    unknownMisses: number // Count of missing values that didn't have a label
}