Split client method docs out of README into docs/

[mike-engel]

The per-method API documentation is growing longer and longer, and with the upcoming push to add 100% API coverage, will make the README massive. This breaks the current API docs out into one guide per client under a new docs/ folder:

- docs/track.md     (TrackClient)
- docs/app.md       (APIClient)
- docs/pipelines.md (PipelinesClient)

The README keeps setup and cross-cutting usage (install, client creation, retries, promise usage) and links to the three guides from a new "API reference" section.

To free the docs/ folder for these hand-written guides, Typedoc's output is repointed from docs/ to typedoc/ (gitignored); .gitignore is updated to match.

AI assisted 🤖

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Note

Low Risk
Documentation and CI-only changes; no library runtime or API behavior is modified.

Overview
Moves per-method API documentation out of the README into committed guides under docs/ (track.md, app.md, pipelines.md, webhooks.md). The README now keeps install, client setup, retries, and promises, with an API reference section linking to those guides and noting npm run docs for Typedoc.

Typedoc output is redirected from docs/ to gitignored typedoc/ so docs/ can hold hand-written guides. typedoc.json registers those guides as projectDocuments, enables githubPages, and drops PushRequestData from intentionallyNotExported.

A new .github/workflows/docs.yml runs on pushes to main (and manual dispatch): npm ci, npm run docs, uploads the typedoc artifact, and deploys to GitHub Pages.

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