- Dart non-api doc pages w/ links to API entries will now have those
links translated from a TS API reference URL to a Dart API reference
URL.
- Created and ran a link checker to verify that all such links to API
entries refer to Dart.
- Fixed links to pages that have moved:
- JS & Dart: `i18n` is under now `cookbook` not `guide`
- Dart: testing page is now directly under guide.
Contributes to #1895Fixes#2273
Patrice Chalin