added some first contributing guidelines and changed the config skeleton

README.md

@@ -293,7 +293,9 @@ So here are some Guidelines.
 
 ## Coding style and linting.
 If you run `nix flake check` there are automated checks in place, please make sure to pass them.
-There is also a code autoformatter (`alejandra`) incorporated into those. You can also install
+There is also a code autoformatter (`alejandra`) incorporated into those. If you want to run
+it you can do so over the development shell or by running `nix fmt`.
+You can also install
 them into your local git repository as pre-commit hooks, and setting up a shell that has
 even more tooling by running `nix develop`. That will give you a bash in which you can run
 all the checks manually `pre-commit run -a`. This will also run the autoformatter.

flake-module.nix

@@ -26,7 +26,6 @@
       ];
     in {
       check.enable = true;
-      pkgs = inputs'.nixpkgs.legacyPackages;
       settings = {
         # for some reason statix takes it config differently than all the other hooks.
         settings.statix = {
@@ -45,6 +44,8 @@
       };
     };
 
+    formatter = pkgs.alejandra;
+
     # Per-system attributes can be defined here. The self' and inputs'
     # module parameters provide easy access to attributes of the same
     # system.