[FEATURE] Support comments for markdown

[Lruihao]

Describe the feature you want 描述你的功能需求

To support an extended markdown format like obsidian comments.

This is an %%inline%% comment.

%%
This is a block comment.

Block comments can span multiple lines.
%%

Useful reference 有价值的参考

{{- /* Comments for Markdown */ -}}
{{- $content = replaceRE "%%(.|\n)*?%%" "" $content -}}
{{- $content = replace $content "<p></p>" "" -}}

• https://gohugo.io/render-hooks/passthrough/
• https://discourse.gohugo.io/t/hey-everyone-i-would-like-to-know-if-it-is-possible-to-support-an-extended-markdown-format-like-obsidian-comments/52321
• https://gohugo.io/content-management/shortcodes/

[Lruihao]

There is no good way to implement it, so let's put it aside for now.