add reusable options menu plugin with localized UI

- Settings autoloads (Game/Input/Graphics/Audio) backed by FileManager,
  persisted to user:// JSON files
- OptionsMenu scene with tabs wired to each autoload: Game (locale),
  Input (invert vertical axis), Graphics (window mode, borderless,
  screen), Audio (master/music/fx volume)
- GraphicsSettings reads DisplayServer state when running in editor
  to avoid clobbering the editor's window mode; exported builds load
  from disk and apply via set_screen_and_apply with a _loading guard
  to suppress redundant writes
- Built-in translations for en/es/fr/de/ja/zh_CN registered at runtime
  from translations/gd_options.csv
- Control-prompt icon assets for keyboard, PlayStation, Xbox, Nintendo
- Flesh out README with scope and audio bus layout requirement

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

translations/gd_options.csv

@@ -0,0 +1,18 @@
+keys,en,es,fr,de,ja,zh_CN
+Game,Game,Juego,Jeu,Spiel,ゲーム,游戏
+Input,Input,Entrada,Entrée,Eingabe,入力,输入
+Graphics,Graphics,Gráficos,Graphismes,Grafik,グラフィック,图像
+Audio,Audio,Audio,Audio,Audio,オーディオ,音频
+Back,Back,Atrás,Retour,Zurück,戻る,返回
+Master,Master,General,Principal,Master,マスター,主音量
+Music,Music,Música,Musique,Musik,音楽,音乐
+FX,FX,Efectos,Effets,Effekte,効果音,音效
+Window Mode,Window Mode,Modo de ventana,Mode de fenêtre,Fenstermodus,ウィンドウモード,窗口模式
+Borderless,Borderless,Sin bordes,Sans bordure,Randlos,ボーダーレス,无边框
+Screen,Screen,Pantalla,Écran,Bildschirm,画面,屏幕
+Windowed,Windowed,Ventana,Fenêtré,Fenster,ウィンドウ,窗口
+Windowed (Maximized),Windowed (Maximized),Ventana (Maximizada),Fenêtré (Maximisé),Fenster (Maximiert),ウィンドウ（最大化）,窗口（最大化）
+Fullscreen,Fullscreen,Pantalla completa,Plein écran,Vollbild,フルスクリーン,全屏
+Invert Vertical Axis,Invert Vertical Axis,Invertir eje vertical,Inverser l'axe vertical,Vertikale Achse umkehren,縦軸を反転,反转垂直轴
+Language,Language,Idioma,Langue,Sprache,言語,语言
+Screen %d,Screen %d,Pantalla %d,Écran %d,Bildschirm %d,画面 %d,屏幕 %d

translations/gd_options.csv.import

@@ -0,0 +1,19 @@
+[remap]
+
+importer="csv_translation"
+type="Translation"
+uid="uid://ve0c3i7bkxwt"
+
+[deps]
+
+files=["res://addons/gd-options/translations/gd_options.en.translation", "res://addons/gd-options/translations/gd_options.es.translation", "res://addons/gd-options/translations/gd_options.fr.translation", "res://addons/gd-options/translations/gd_options.de.translation", "res://addons/gd-options/translations/gd_options.ja.translation", "res://addons/gd-options/translations/gd_options.zh_CN.translation"]
+
+source_file="res://addons/gd-options/translations/gd_options.csv"
+dest_files=["res://addons/gd-options/translations/gd_options.en.translation", "res://addons/gd-options/translations/gd_options.es.translation", "res://addons/gd-options/translations/gd_options.fr.translation", "res://addons/gd-options/translations/gd_options.de.translation", "res://addons/gd-options/translations/gd_options.ja.translation", "res://addons/gd-options/translations/gd_options.zh_CN.translation"]
+
+[params]
+
+compress=1
+delimiter=0
+unescape_keys=false
+unescape_translations=true