feat: update docs via LLM (#216)

overlays/README.md

@@ -5,7 +5,46 @@ Overlays for both NixOS and Nix-Darwin.
 If you don't know much about overlays, it is recommended to learn the function and usage of overlays
 through [Overlays - NixOS & Flakes Book](https://nixos-and-flakes.thiscute.world/nixpkgs/overlays).
 
-1. `default.nix`: the entrypoint of overlays, it execute and import all overlay files in the current
-   directory with the given args.
-2. `fcitx5`: fcitx5's overlay, add my customized Chinese input method -
-   [小鹤音形输入法](https://flypy.com/)
+## Current Structure
+
+```
+overlays/
+├── README.md
+├── default.nix          # Entrypoint for all overlays
+└── fcitx5/              # Chinese input method configuration
+    ├── README.md
+    ├── default.nix      # fcitx5 overlay definition
+    └── rime-data-flypy/ # Custom rime data for 小鹤音形输入法
+        └── share/
+            └── rime-data/
+                ├── build/
+                ├── default.custom.yaml
+                ├── default.yaml
+                ├── flypy.schema.yaml
+                ├── flypy_full全码字.txt
+                ├── flypy_sys.txt
+                ├── flypy_top.txt
+                ├── flypy_user.txt
+                ├── lua/
+                │   └── calculator_translator.lua
+                ├── rime.lua
+                ├── squirrel.custom.yaml
+                └── squirrel.yaml
+```
+
+## Components
+
+### 1. `default.nix`
+
+The entrypoint of overlays, it execute and import all overlay files in the current directory with
+the given args.
+
+### 2. `fcitx5`
+
+fcitx5's overlay, add my customized Chinese input method - [小鹤音形输入法](https://flypy.com/)
+
+This overlay provides:
+
+- Custom rime data for 小鹤音形输入法 (Flypy input method)
+- Cross-platform support for both Linux (fcitx5-rime) and macOS (squirrel)
+- Pre-configured input method settings