treewide: begin restructuring the module tree

modules/plugins/languages/markdown/config.nix

@@ -0,0 +1,40 @@
+{
+  pkgs,
+  config,
+  lib,
+  ...
+}: let
+  inherit (lib.nvim.lua) expToLua;
+  inherit (lib.modules) mkIf mkMerge;
+  inherit (lib.lists) isList;
+
+  cfg = config.vim.languages.markdown;
+  servers = {
+    marksman = {
+      package = pkgs.marksman;
+      lspConfig = ''
+        lspconfig.marksman.setup{
+          capabilities = capabilities;
+          on_attach = default_on_attach;
+          cmd = ${
+          if isList cfg.lsp.package
+          then expToLua cfg.lsp.package
+          else ''{"${cfg.lsp.package}/bin/marksman", "server"}''
+        },
+        }
+      '';
+    };
+  };
+in {
+  config = mkIf cfg.enable (mkMerge [
+    (mkIf cfg.treesitter.enable {
+      vim.treesitter.enable = true;
+      vim.treesitter.grammars = [cfg.treesitter.mdPackage cfg.treesitter.mdInlinePackage];
+    })
+
+    (mkIf cfg.lsp.enable {
+      vim.lsp.lspconfig.enable = true;
+      vim.lsp.lspconfig.sources.markdown-lsp = servers.${cfg.lsp.server}.lspConfig;
+    })
+  ]);
+}