gd: added menu template

addons/maaacks_game_template/docs/GameSaving.md

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+# Game Saving
+
+> [!IMPORTANT]  
+> The save system doesn't follow the same conventions as other systems.  
+> It is subject to change.  
+
+> [!WARNING]  
+> The save system relies on resource files, which are vulnerable to having malicious scripts injected into them.  
+> Please discourage players from sharing their save files. Do not use this for cloud saving, either.  
+> A safer save system is planned.  
+
+
+The templates and plugin suite aim to keep most class definitions within the addon. These are not usually expected change. Unlike the other classes, the `GameState` and `LevelState` are defined for the developer to edit to their needs.
+
+## Usage
+
+The `GlobalState` static class keeps the state saved to a resource. The developer is responsible for making sure `GlobalState.save()` gets called when they want the state saved to the disk.  
+
+### Game State
+
+The `GameState` class represents the state of a single playthrough of the game. It currently stores the current level, the max level reached, and the state of each level currently visited.
+
+It is currently expected to be used as a singleton, too.
+
+
+### Level State
+
+The `LevelState` class represents the state of a single level in a playthrough of the game. It currently stores whether the tutorial has been read, and a color, if the player has set one in the example levels.  It can be used to store the states of many other level specific features.
+
+From within the `_ready()` method of a level scene, call `GameState.get_level_state(scene_file_path)` to get the last saved `LevelState`, or a new one, and then set the state of the level from that. When a state of the level changes that is intended to be preserved, save it into the level state, and call `GlobalState.save()`.
+
+Examples are provided allowing the player to save the level background color, and keeping the tutorial message from popping up more than once per playthrough.