Add FAQ section with troubleshooting checklists

[pfefferle]

Proposed changes:

• Add a new docs/faq/ section with checklists for the two most common support topics, distilled from recurring wordpress.org support threads and GitHub issues:
  • Why is a follow request stuck on "pending"? — splits triage into inbound causes (host mod_security rules, REST-restricting security plugins, caching/Cloudflare, signature 401s, the Disallowed Comment Keys list) and outbound causes (WP-Cron, blocked outgoing requests), including a ready-to-send host-escalation template and Mastodon delivery-failure-tracking recovery.
  • Why don't comments from the Fediverse show up? — Spam/Pending/Trash first, then the captcha/antispam plugin class (hCaptcha, Advanced Google reCAPTCHA, WP Armour, CleanTalk, Akismet quirks), silently-discard options, and protocol semantics (mentions without inReplyTo).
• Cross-link the new section from docs/readme.md, docs/how-to/readme.md and the readme.txt FAQ.
• Every cause listed is backed by maintainer-confirmed forum threads or GitHub issues and was verified against the current code paths (Moderation disallowed-list check, Interactions::persist() comment pipeline, auto-accepted follows).

Other information:

• Have you written new tests for your changes, if applicable? (not applicable, documentation only)

Testing instructions:

• Read both new guides in docs/faq/ and check the advice against your support-thread experience.
• Verify the relative links between docs/faq/, docs/how-to/ and the GitHub links in readme.txt resolve.

[Copilot]

Pull request overview

This PR adds a new troubleshooting-oriented FAQ documentation section and links to it from existing user-facing docs/readmes, to make the most common support resolutions easier to find.

Changes:

• Add docs/faq/ with two checklist-style troubleshooting guides (pending follows; missing federated comments).
• Cross-link the new FAQ section from docs/readme.md, docs/how-to/readme.md, and the plugin readme.txt.
• Add a patch-level changelogger entry announcing the new FAQ guides.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
readme.txt	Updates the “How do I solve…” FAQ pointer to include the new docs FAQ section and examples.
docs/readme.md	Adds a top-level “FAQ” section linking to the new troubleshooting docs.
docs/how-to/readme.md	Cross-links to the FAQ for “something broken” troubleshooting before configuration guides.
docs/faq/readme.md	Introduces the FAQ landing page and table of contents.
docs/faq/pending-follow-requests.md	New troubleshooting checklist for diagnosing pending follow requests (inbound vs outbound).
docs/faq/missing-comments.md	New troubleshooting checklist for missing federated comments (queues, captcha/antispam, inbox blocking, semantics).
.github/changelog/add-troubleshooting-faq	Changelogger entry for the added FAQ guides.