Add conform plugin

modules/home-manager/nixvim/plugins/conform.nix

@@ -0,0 +1,42 @@
+{ ... }:
+
+{
+  programs.nixvim = {
+    extraPackages = with pkgs; [
+      stylua
+    ];
+
+    plugins.conform-nvim = {
+      enable = true;
+      notifyOnError = false;
+      formatOnSave = ''
+        function(bufnr)
+          local disable_filetypes = { c = true, cpp = true }
+          return {
+            timeout_ms = 500
+            lsp_fallback = not disable_filetypes[vim.bo[bufnr].filetype]
+          }
+        end
+      '';
+
+      formattersByFt = {
+        lua = ["stylua"];
+      };
+    };
+
+    keymaps = [
+      {
+        mode = "";
+        key = "<leader>f";
+        action.__raw = ''
+          function()
+            require('conform').format { async = true, lsp_fallback = true }
+          end
+        '';
+        options = {
+          desc = "[F]ormat buffer";
+        };
+      }
+    ];
+  };
+}