nixvim: support highlight groups

modules/highlights.nix

@@ -0,0 +1,30 @@
+{ config, lib, helpers, ... }:
+with lib;
+{
+  options = {
+    highlight = mkOption {
+      type = types.attrsOf types.anything;
+      default = { };
+      description = "Define highlight groups";
+      example = ''
+        highlight = {
+          Comment.fg = '#ff0000';
+        };
+      '';
+    };
+  };
+
+  config = mkIf (config.highlight != { }) {
+    extraConfigLuaPost = ''
+      -- Highlight groups {{
+      do
+        local highlights = ${helpers.toLuaObject config.highlight}
+
+        for k,v in pairs(highlights) do
+          vim.api.nvim_set_hl(0, k, v)
+        end
+      end
+      -- }}
+    '';
+  };
+}