feat: add comments, format all nix files

overlays/default.nix

@@ -1,6 +1,6 @@
 args:
-  # execute and import all overlay files in the current directory with the given args
-  builtins.map
+# execute and import all overlay files in the current directory with the given args
+builtins.map
   (f: (import (./. + "/${f}") args))  # execute and import the overlay file
   (builtins.filter          # find all overlay files in the current directory
     (f: f != "default.nix")

overlays/fcitx5/default.nix

@@ -1,6 +1,6 @@
 # 为了不使用默认的 rime-data，改用我自定义的小鹤音形数据，这里需要 override
 # 参考 https://github.com/NixOS/nixpkgs/blob/e4246ae1e7f78b7087dce9c9da10d28d3725025f/pkgs/tools/inputmethods/fcitx5/fcitx5-rime.nix
-{...}: 
+{ ... }:
 
 (self: super: {
   # 小鹤音形配置，配置来自 flypy.com 官方网盘的鼠须管配置压缩包「小鹤音形“鼠须管”for macOS.zip」