[V2] Adding "Draft" header option for Blog

[tomtongue]

🚀 Feature

Draft post mode for Blog such as draft: true
This option enable to avoid publishing a post if the post has draft: true in the Header option.

Currently, Header options for Blog does not support "draft" tag such as that of Jekyll; Posts | Jekyll • Simple, blog-aware, static sites, as shown in Blog | Docusaurus.

Have you read the Contributing Guidelines on issues?

Yes.

Motivation

Docusaurus enables us to create one of the most beautiful and useful documentation and blog site. However, when we use this as a Blog site and try to create a new blog post, we need to create a (or some) new branch(es) and then merge the master branch (as one of the example). It need more steps, compared with Jekyll. This functionality should help many users.

Pitch

Draft mode provides more easily to use it by blog user, team and so on.

• Providing more easy publish
• More easy to manage posts
• Possibly avoiding to create many branches

[lex111]

You can create any directory (for example, drafts) in the directory with the blog posts (blog) and move posts there that should not be published yet (blog/drafts/post.md).

[yangshun]

I think they want to be able to preview drafts during dev as well. I remember trying to implement drafts before but wasn't too successful due to how the tags data was processed. Not against this idea and following the Jekyll convention would be good.

[tomtongue]

Thank you! Yes, currently, I'll create drafts directory and put drafts on the directory. Do you think it is needed to add the current document? If needed, I'll send pull request for this.