feat(fmt): Add formatter using alejandra and format flake

flake.nix

@@ -38,6 +38,10 @@
 
     # This is where the Neovim derivation is built.
     neovim-overlay = import ./nix/neovim-overlay.nix {inherit inputs;};
+    inherit (self) outputs;
+    # This is a function that generates an attribute by calling a function you
+    # pass to it, with each system as an argument
+    forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
   in
     flake-utils.lib.eachSystem supportedSystems (system: let
       pkgs = import nixpkgs {
@@ -66,6 +70,7 @@
         '';
       };
     in {
+      formatter = nixpkgs.legacyPackages.${system}.alejandra;
       packages = rec {
         default = nvim;
         nvim = pkgs.nvim-pkg;

nix/cpptools.nix

@@ -1,13 +1,14 @@
-{ stdenv, lib
-, system ? builtins.currentSystem
-, fetchurl
-, unzip
-, libz
-, libcxx
-, lttng-ust_2_12
-, autoPatchelfHook
+{
+  stdenv,
+  lib,
+  system ? builtins.currentSystem,
+  fetchurl,
+  unzip,
+  libz,
+  libcxx,
+  lttng-ust_2_12,
+  autoPatchelfHook,
 }:
-
 stdenv.mkDerivation rec {
   pname = "cpptools";
   version = "1.21.6";
@@ -20,7 +21,6 @@ stdenv.mkDerivation rec {
   darwin-x64 = "https://github.com/microsoft/vscode-cpptools/releases/download/v${version}/cpptools-macos-x64.vsix";
   darwin-arm64 = "https://github.com/microsoft/vscode-cpptools/releases/download/v${version}/cpptools-macos-arm64.vsix";
 
-
   src = fetchurl {
     url = lib.getAttr system {
       x86_64-linux = "https://github.com/microsoft/vscode-cpptools/releases/download/v${version}/cpptools-linux-x64.vsix";