Add markdown devshell

devshells/markdown.nix

@@ -0,0 +1,25 @@
+{
+  withSystem,
+  inputs,
+  ...
+}: {
+  perSystem = {
+    config,
+    pkgs,
+    lib,
+    inputs',
+    ...
+  }: {
+    devShells.markdown = pkgs.mkShell {
+      buildInputs = with pkgs; [
+        (python3.withPackages (ps:
+          with ps; [
+            mdformat
+            mdformat-gfm
+            mdformat-tables
+            mdformat-footnote
+          ]))
+      ];
+    };
+  };
+}

flake.nix

@@ -36,6 +36,7 @@
         ./devshells/rust.nix
         ./devshells/idris2.nix
         ./devshells/raku.nix
+        ./devshells/markdown.nix
       ];
       config = {
         systems = [