add markdown to checks

Signed-off-by: ahuston-0 <aliceghuston@gmail.com>

.mdl_style.rb

@@ -1,5 +0,0 @@
-#!/usr/bin/env ruby
-
-all
-rule 'MD007', :indent => 2
-rule 'MD013', :tables => false

checks.nix

@@ -4,7 +4,12 @@
   formatter,
   ...
 }:
-forEachSystem (system: {
+forEachSystem (
+  system:
+  let
+    pkgs = inputs.nixpkgs.legacyPackages.${system};
+  in
+  {
     pre-commit-check = inputs.pre-commit-hooks.lib.${system}.run {
       src = ./.;
       hooks = {
@@ -46,11 +51,13 @@ forEachSystem (system: {
         # markdown hooks
         mdl = {
           enable = true;
-        settings.rules = [
-          "all"
-          "rule 'MD007', :indent => 2"
-          "rule 'MD013', :tables => false"
-        ];
+          settings.style =
+            (pkgs.writeText ".mdl_style.rb" ''
+              #!/usr/bin/env ruby
+
+              all
+              rule 'MD013', :tables => false
+            '').outPath;
         };
 
         # git hooks
@@ -65,4 +72,5 @@ forEachSystem (system: {
         detect-private-keys.enable = true;
       };
     };
-})
+  }
+)