feat: ship the interface in eight languages, with per-language plurals and mirroring

app/locales/en-US/main.ftl

@@ -138,6 +138,21 @@ settings-variant-warm = Warm
 settings-variant-cool = Cool
 settings-variant-green = Green
 settings-variant-mono = Mono
+settings-language-heading = Language
+settings-language-system = Follow system
+
+## Languages
+
+# Every language is named in its own words, so a reader who cannot read the
+# current interface can still find theirs. Leave these untranslated.
+language-en = English
+language-de = Deutsch
+language-es = Español
+language-fr = Français
+language-he = עברית
+language-ja = 日本語
+language-pt = Português
+language-ru = Русский
 
 ## Forms