Consider making `web-mode-comment-insert` engine aware

[lljr]

When editing a handlebars buffer like this
(| determines the current cursor position)

|
{{#if this.isOk}}
<p>Hello</p
{{/if}}

and then M-; it inserts a <!-- --> style comment, but I want {{!-- --}}.

Looking at web-mode-comment-insert, this could be added

     (t
      (cond
       ((string= web-mode-engine "ctemplate")
        (insert "{{!-- --}}")
        (search-backward "--}}"))
       (progn
         (insert "<!--  -->")
         (search-backward " -->")))
      ) ;case html

in

(defun my-web-mode-comment-insert ()
  (let ((alt nil)  (pos 22) (web-mode-engine "ctemplate"))
    (cond
     ((get-text-property pos 'block-side)
      (cond
       ((and alt (string= alt "//"))
        (insert "// "))
       (t
        (insert "/*  */")
        (search-backward " */"))
       ) ;cond
      ) ;case block-side
     ((get-text-property pos 'part-side)
      (cond
       ((and alt (string= alt "//"))
        (insert "// "))
       (t
        (insert "/*  */")
        (search-backward " */"))
       ) ;cond
      ) ;case part-side
     (t
      (cond
       ((string= web-mode-engine "ctemplate")
        (insert "{{!-- --}}")
        (search-backward "--}}"))
       (progn
         (insert "<!--  -->")
         (search-backward " -->")))
      ) ;case html
     ) ;cond
    ))

I hard-coded the variables in the last code block to do a quick test. I also deleted references to language since this was only used to print a message, which was commented out.

I see there is web-mode-comment-style which could be used with web-mode-engine-alist to loop through all the atoms and then compare to grab the match, to finally access web-mode-comment-style to insert the comment according to its engine.

Thoughts?