Editor setup has moved 📦

Our editor setup guide now lives in the Project Sidewalk repository, and it now covers both IntelliJ IDEA and VS Code (the team uses both — we mandate neither):

➡️ docs/editor-setup.md

It covers the JDK (Java 17), the IntelliJ Scala/Play/HOCON/i18n plugins, the VS Code Metals extension, and format-on-save with scalafmt.

Please update your bookmarks. This page is kept only as a redirect. See issue #4252 for why we moved core developer docs into the repo.