Add Expo Universal Links Doctor - #1253

Adds one entry to Development Tools > Debugging: Expo Universal Links Doctor (https://arling.sk/expo-universal-links-doctor/).

What it does: you paste your app.json (associatedDomains / intentFilters), your hosted apple-app-site-association file, and assetlinks.json, and it cross-checks them against what iOS and Android verification actually require, reporting the exact reason a https:// link opens a browser tab instead of the app (missing applinks: prefix, AASA served with a redirect, assetlinks.json not a JSON array, package/team ID mismatches, etc.).

• Runs entirely in the browser (static site, no backend, no network calls). Nothing you paste is sent to a server.
• Free, no signup.
• Analytics: anonymous visit/click counts only, via a self-hosted Umami instance — no tracking of what you paste.
• Maintained by ARLing s. r. o. (Bratislava, Slovakia). It's source-visible (view-source is the whole client-side app) but not under an OSS license — all rights reserved.

This is a new tool (shipped this week) rather than one with an established user base, so I'm flagging that plainly rather than overstating adoption — happy to have it held to the same bar as everything else per CONTRIBUTING.md.

Added at the end of the Debugging list (the list isn't alphabetized), format [NAME](LINK) - Description. per CONTRIBUTING.md.