feat: refine group (fix#287)

[zyy7259]

Summary

• isolate a group's open status with isolated: true
• config a isolated group's initial open status with initialIsolatedOpen: true
• config a group's sidebarDepth with sidebarDepth: 2
• nested sidebar groups

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Build-related changes
• Other, please describe:

If changing the UI of default theme, please provide the before/after screenshot:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)

You have tested in the following browsers: (Providing a detailed version will be better.)

os: Mac High Sierra 10.13.6

• Chrome Version 67.0.3396.99 (Official Build) (64-bit)
• Firefox 60.0.2 (64-bit)
• Safari Version 11.1.2 (13605.3.8)
• Edge
• IE

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature
• Related documents have been updated
• Related tests have been updated

To avoid wasting your time, it's best to open a feature request issue first and wait for approval before working on it.

Other information:

[zyy7259]

Test demo urls:

• https://zyy7259.github.io/test-vuepress-nested-group/nested/
• https://zyy7259.github.io/test-vuepress-nested-group/zh/nested/

If you want to build the demo from scratch:

• git clone git@github.com:zyy7259/vuepress.git
  • cd vuepress
  • yarn
  • git checkout feature-refine-group
• cd ..
• git clone git@github.com:zyy7259/test-vuepress-nested-group.git
  • cd test-vuepress-nested-group
  • npm run dev

[davestewart]

What does this mean / do?

You can isolate a group's open status with isolated: true

[zyy7259]

What does this mean / do? ...

@davestewart Right now, when you open a group, other groups will be closed automatically. With isolated: true a group won’t be closed when you open another group at the same level.

[marceloavf]

Looking forward for this, need any help?

[zyy7259]

Rebased from master.

Should I wait and rebase again when #815 is done?

[jackpope]

@zyy7259 Looks like #815 was merged. Do you need anything on this?

[zyy7259]

Rebased on top of master.

[rasapetter]

This change is probably not relevant for this PR?

[zyy7259]

Oh, I have config my IDE to trim trailing whitespace. Should I add the whitespace back?

[ulivz]

Thanks for the great work, but it's not recommended to bundle two many features in a PR.

I just create a PR containing following necessary features:

1. Configurable sidebarDepth for sidebar group;
2. Nested sidebar groups;
3. Clickable heading for sidebar groups.

For isolated and initialIsolatedOpen, they are not so necessary, but will bring much extra learning costs, therefore we are not going to introduce these features.

Let's move #1257 to continue.