pub fn install(default: &str, locales: &[(&str, &str)])Expand description
Register an app’s locales from .ftl sources and set the current locale from (1) the DAY_LOCALE
launch override, (2) the platform’s set_launch_locale hint, (3) default. Call once, before
building the root piece. The built-in core catalog is preserved (and remains the fallback); the
app’s strings take precedence over it, and re-registering reuses the existing locale [Signal]
so bindings created earlier keep working.