feat: Add frandroid.com custom parser

[jocmp]

Summary

• Adds a custom mercury-parser extractor for www.frandroid.com to address jocmp/capyreader#1721 ("half of articles don't show at all in full content").
• Pulls article body from section.article-content (single selector) so the article wrapper is consistently picked up regardless of layout, with newsletter/related/ad blocks cleaned out.
• Uses meta tags for title, date, dek, and lead image. Author falls back to parsely-author because the page emits multiple meta[name="author"] tags which Mercury's meta extractor skips.

Test plan

• npx jest src/extractors/custom/www.frandroid.com/index.test.js passes (7/7)
• Verify in capyreader against a sample of articles from http://feeds.feedburner.com/frandroid

Refs jocmp/capyreader#1721