docs: add Interceptors API reference page

[enjoykumawat]

Summary

• Adds docs/docs/api/Interceptors.md — a comprehensive API reference for all eight built-in interceptors (dump, retry, redirect, decompress, responseError, dns, cache, deduplicate), covering constructor options, defaults, per-request overrides, and usage examples.
• Updates docs/docs/site.json to include the new page in the sidebar under a dedicated Interceptors group (between Proxy & Agents and Handlers).

Closes #886 (connect option needs more tests and docs — the connect option documentation gap is part of the broader missing interceptors docs).

What changed

docs/docs/api/Interceptors.md — new file documenting:

• interceptors.dump([opts]) — maxSize, per-request dumpMaxSize override
• interceptors.retry([opts]) — links to RetryHandler options
• interceptors.redirect([opts]) — maxRedirections, throwOnMaxRedirect, stripHeadersOnRedirect, stripHeadersOnCrossOriginRedirect
• interceptors.decompress([opts]) — skipStatusCodes, skipErrorResponses, experimental warning note
• interceptors.responseError([opts]) — error body decoding behaviour
• interceptors.dns([opts]) — maxTTL, maxItems, dualStack, affinity, custom lookup/pick/storage
• interceptors.cache([opts]) — links to CacheStore docs
• interceptors.deduplicate([opts]) — methods, skipHeaderNames, excludeHeaderNames, maxBufferSize
• Composing multiple interceptors (ordering guidance + end-to-end example)

docs/docs/site.json — adds { "link": "/api/Interceptors", "label": "Interceptors" } under a new Interceptors sidebar group.

Test plan

• Verify markdown renders correctly in the docs site
• Check all option names match the TypeScript definitions in types/interceptors.d.ts
• Confirm sidebar link resolves to the new page

[metcoder95]

I'm +1 on moving the interceptors docs in a new place, but we need to also cleanup what is in the Dispatcher section; just keeping the description of the Dispatcher#compose and how does, and linking the interceptors list to this

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.47%. Comparing base (0f1f890) to head (fbac28a).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5446   +/-   ##
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  Coverage   93.46%   93.47%           
=======================================
  Files         110      110           
  Lines       37106    37106           
=======================================
+ Hits        34682    34684    +2     
+ Misses       2424     2422    -2     

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