fix(io): re-export public type aliases

[jsejcksn]

This PR re-exports type aliases used by parameters in exported functions — which the consumer would otherwise have to locate and import from a separate module.

For example, to include the parameter type WriterSync used by writeAllSync:

export function writeAllSync(writer: WriterSync, data: Uint8Array) { … }

Source

…before this PR the user would need to write:

import { writeAllSync } from "@std/io/write-all";
import type { WriterSync } from "@std/io/types";

…after the user would need to write:

import { writeAllSync, type WriterSync } from "@std/io/write-all";

---

Ref: Query for similar previous PRs from me

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.08%. Comparing base (062aa94) to head (66bed62).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6969   +/-   ##
=======================================
  Coverage   94.08%   94.08%           
=======================================
  Files         600      600           
  Lines       43553    43553           
  Branches     6997     6997           
=======================================
  Hits        40977    40977           
  Misses       2521     2521           
  Partials       55       55           

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[kt3k]

LGTM