home: move flake to root of directory

Reason is that I cannot reference any file (also in home.file) which is
located above (../) the flake file

flake.nix

@@ -0,0 +1,48 @@
+{
+  description = "Home Manager configuration of julian";
+
+  inputs = {
+    nixpkgs-stable.url = "github:nixos/nixpkgs/nixos-23.11";
+    nixpkgs-unstable.url = "github:nixos/nixpkgs/nixos-unstable";
+
+    home-manager = {
+      url = "github:nix-community/home-manager/release-23.11";
+      inputs.nixpkgs.follows = "nixpkgs-stable";
+    };
+
+    alacritty-theme = {
+      url = "github:alacritty/alacritty-theme";
+      flake = false;
+    };
+  };
+
+  outputs = { nixpkgs-stable, nixpkgs-unstable, home-manager, ... }@inputs:
+    let
+      system = "x86_64-linux";
+
+      unstable-overlay = final: prev: {
+        unstable = import nixpkgs-unstable {
+          inherit system;
+          config.allowUnfree = true;
+        };
+      };
+
+      pkgs = import nixpkgs-stable {
+        inherit system;
+        config.allowUnfree = true;
+        overlays = [ unstable-overlay ];
+      };
+    in {
+      homeConfigurations."julian" = home-manager.lib.homeManagerConfiguration {
+        inherit pkgs;
+
+        # Specify your home configuration modules here, for example,
+        # the path to your home.nix.
+        modules = [ ./home-manager/home.nix ];
+
+        # Optionally use extraSpecialArgs
+        # to pass through arguments to home.nix
+        extraSpecialArgs = { inherit inputs; };
+      };
+    };
+}