chore: use Primitive type from type-fest (#820)

This types-only change removes a custom `Primitive` type in favor of
type-fest's.

We defined them the same way so it shouldn't make a difference.

src/lib/hashmap.js

@@ -1,4 +1,4 @@
-/** @typedef {string | number | bigint | boolean | undefined | symbol | null} Primitive */
+/** @import { Primitive } from 'type-fest' */
 
 /**
  * `Map` uses same-value-zero equality for keys, which makes it more difficult