docs: add FTW Discord invite

[frahlg]

Problem and result

The README has no Discord invite. Add the owner's invite beside the community information so readers can find FTW discussions and ask questions.

Scope and safety

README only. The open README change in #1051 adds a link to the documentation list; this addition is in a separate section.

Verification

git diff --check passes. Checked the invite URL against the owner's request. No runtime code changed.

Checklist

• The change follows VISION.md and one selected scope.
• I checked overlapping PRs and kept the README additions separate.
• Relevant checks cover the change.
• No UI changed.
• Documentation-only change; no Changeset required.
• Every commit has a DCO sign-off.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-28T17:29:39.655412Z	ff5fd12	PR opened

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