docs(net): expand @cacheable/net README with full API, Features, and Table of Contents (#1666)

* docs(net): expand @cacheable/net README with full API, Features, and Table of Contents

Restructure the README to mirror the cacheable package README:
- Expanded Features list
- Full Table of Contents with working anchors
- Document HTTP method helpers, DataResponse shape, fetch usage,
  caching control, RFC 7234 semantics, simple caching mode, custom
  serialization, error handling, custom/shared cache, and events
- Document standalone functions (fetch/get/post/patch/del/head)
- Full WHOIS and RDAP reference: options tables, result type shapes,
  and exported parsing helpers
- Add CacheableNet options, API, and exports/types reference sections

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ERPCDjhDCjXjwrAkBD9z3Y

* docs(net): correct caching claims and standalone helper usage in README

Apply accuracy fixes found via source verification and PR review:
- Only GET is cached by default and only PUT supports per-request
  caching (caching: true); POST/PATCH/DELETE/HEAD are never cached at
  the fetch layer, so the caching option has no effect on them
- Note that PUT cache identity is method + URL only (body is not part
  of the cache key)
- Scope request coalescing to simple caching mode and WHOIS/RDAP
  lookups (the default RFC 7234 path does not coalesce)
- Clarify that standalone get/post/patch/head require an options
  argument and del requires an options object (they throw otherwise)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ERPCDjhDCjXjwrAkBD9z3Y

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: jaredwray