Add support for 'reset value of face attribute

[binarin]

Newer emacs introduces new possible value for the face attributes - 'reset.

This is from the elisp manual from the fresh git emacs:

A face attribute can also have the value ‘reset’.  This special value
stands for the value of the corresponding attribute of the ‘default’
face.

Also it looks like this is yet unhandled problem for the
htmlfontify-buffer included in emacs itself: https://lists.gnu.org/archive/html/bug-gnu-emacs/2026-05/msg00923.html

[binarin]

And this is a temporary workaround that can be added to a emacs config:

(advice-add 'htmlize-face-color-internal :around
            (defun b/htmlize-face-reset-workaround (orig-fun face bg)
              (pcase (funcall orig-fun face bg)
                ('reset (funcall orig-fun 'default bg))
                (val))))