Add support for collapsible multi-level sidebar

[LittleSound]

Is your feature request related to a problem? Please describe.

I would like to have to collapsible navigation sidebar since I organize my documents by using multiple layers of folders, which is frustrating to browse or lookup the content/page I want.

VitePress only supports the top-level folders to be collapsible in the navigation sidebar currently.

Describe the solution you'd like

The default theme that VitePress provided could support multi-level sidebar to be collapsible since many of the people may also face such kind of the problem while using VitePress.

Describe alternatives you've considered

I have tried to override the VPSidebarNav component from default theme that VitePress provided, however, the theme configuration overridding is not supported currently (related issue is still open, ref: #235 ), or I would have to duplicate the default theme as a single repository and publish it as a npm package after the development is done by myself. Anyways, I may think this kind of the feature is general for most of the users, it should be provided by VitePress, nor by users.

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the docs.
• Read the Contributing Guidelines.
• Check that there isn't already an issue that asks for the same feature to avoid creating a duplicate.

[awbait]

How can I collapse this item?

[nekomeowww]

This kind of feature is awesome, I would really need it!
Do you guys have a roadmap or plan for when the feature would be released?

[brc-dd]

I'm currently working on the code groups feature, will review and try to get #1361 merged within this week. Sorry for the delay 😓

[kiaking]

I'll take that PR over to adjust the design a bit 👍

[Goozoon]

I'll take that PR over to adjust the design a bit 👍

Great. Please add (i think it is called --vp-c-brand element) so it will look something like this

We have it already for the right side 'on this page' already. For that part i would add some padding under 'on this page' text and some multileveling for the rest. Something like this but in Vitepress style

Thank you Kia King

[awbait]

we are looking forward to it

[mrcego]

Waiting for this. In the company I'm currently working we are populating a doc with Vitepress, and we need three levels of categories in one of the team page.

[Zhengqbbb]

Expecting and waiting for this. I think the next step should be to push this feature.