Hide markup even if markdown-fontify-whole-heading-line is enabled

[kuranari]

Description

Hide markup even if markdown-fontify-whole-heading-line is enabled.

(set-face-attribute 'markdown-header-face-1 nil :height 1.5 :background "pink" :extend t)
(set-face-attribute 'markdown-header-delimiter-face nil :background "green" :extend t)

Closing tag is present

# Headline #

	markdown-fontify-whole-heading-line: t	markdown-fontify-whole-heading-line: nil
Markdown-hide-markup: t
Markdown-hide-markup: nil

Closing tag is not present

# Headline

	markdown-fontify-whole-heading-line: t	markdown-fontify-whole-heading-line: nil
Markdown-hide-markup: t
Markdown-hide-markup: nil

Screenshot script

```elisp ;; This code depends on the 'screencapture' utility of macOS. (dolist (fontify-whole-line '(nil t)) (dolist (markup-hiding '(-1 +1)) (setq markdown-fontify-whole-heading-line fontify-whole-line) (markdown-toggle-markup-hiding markup-hiding) (sit-for 0.1) (let ((filename (format "~/screencapture-markdown-fontify-whole-heading-line-%s-markdown-hide-markup-%s.png" fontify-whole-line markup-hiding))) (shell-command (concat "screencapture " filename))))) ```

Related Issue

https://github.com/jrblevin/markdown-mode/issues/773

Type of Change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [X] Improvement (non-breaking change which improves an existing feature)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• [X] I have read the CONTRIBUTING.md document.
• [X] I have updated the documentation in the README.md file if necessary.
• [X] I have added an entry to CHANGES.md.
• [X] I have added tests to cover my changes.
• [X] All new and existing tests passed (using make test).

[kuranari]

I'm not certain about the behavior(especially when the closing tag is present). Please feel free to comment :)

[syohex]

I think it looks good thanks