ui/hl-todo: fix comment detection for some major modes

For major modes with poorly implemented syntax-tables, or simply can't
use them for their comments.

modules/ui/hl-todo/autoload.el

@@ -0,0 +1,14 @@
+;;; ui/hl-todo/autoload.el -*- lexical-binding: t; -*-
+
+;;;###autoload
+(defun +hl-todo|use-face-detection ()
+  "Use a different, more primitive method of locating todo keywords.
+
+This is useful for major modes that don't use or have a valid syntax-table entry
+for comment start/end characters."
+  (set (make-local-variable 'hl-todo-keywords)
+       `(((lambda (limit)
+            (let (case-fold-search)
+              (and (re-search-forward hl-todo-regexp limit t)
+                   (memq 'font-lock-comment-face (doom-enlist (get-text-property (point) 'face)))))
+            (1 (hl-todo-get-face) t t))))))