docs(readme): add ActivityWatch context

[TimeToBuildBob]

Closes #204

Summary

• explain what aw-watcher-web adds beyond desktop window-title tracking
• link readers to the watchers, architecture, and buckets/events docs

Testing

• verified the new docs links return HTTP 200
• pre-commit hooks in the repo passed during commit

[greptile-apps]

Greptile Summary

This PR adds a brief introductory paragraph and "Learn more" links to README.md, clarifying what aw-watcher-web contributes beyond desktop window-title tracking. No code is changed.

• Adds a two-sentence description of the extension's tracked fields (title, URL, audible state, incognito state) and how they complement the desktop watchers.
• Adds three reference links to the ActivityWatch documentation (watchers, architecture, buckets/events) as a "Learn more" nav line near the top of the README.

Confidence Score: 5/5

Safe to merge — the change is limited to two new sentences and three reference links in the README with no code modifications.

The diff touches only README.md with purely additive prose and three documentation URLs. The new text accurately reflects what the extension records and the links point to the official ActivityWatch docs.

No files require special attention.

Important Files Changed

Filename	Overview
README.md	Documentation-only change: adds a context paragraph and three docs links; no functional code affected.

Sequence Diagram

sequenceDiagram
    participant Browser
    participant aw-watcher-web
    participant ActivityWatch

    Browser->>aw-watcher-web: Tab becomes active (title, URL, audible, incognito)
    aw-watcher-web->>ActivityWatch: POST heartbeat event to bucket
    ActivityWatch-->>aw-watcher-web: 200 OK

    note over Browser,ActivityWatch: Without aw-watcher-web, ActivityWatch desktop<br/>watchers only see the browser window title

Loading

_{Reviews (1): Last reviewed commit: "docs(readme): add ActivityWatch context" | Re-trigger Greptile}

[TimeToBuildBob]

CI is green and this PR is ready to merge. I attempted to merge it, but TimeToBuildBob does not have merge permission on this repo and auto-merge is not enabled here.