Docsify: Add the ability to fold code

[mraiguo]

Feature request

Add the ability to fold code， can add an expanded icon to the right

What problem does this feature solve?

Page code is too much to expand when you don't need it

What does the proposed API look like?

maybe a plugin?

How should this be implemented in your opinion?

just add a config

Are you willing to work on this yourself?

I will try If you have the time

[Koooooo-7]

Actually，I guess you can use <details> tag to do this.

<details>
<summary>tab name</summary>
your markdown code block.
</details>

tab name

your markdown code block.