Provide expand all | collapse all buttons

[wajihaparvez]

Describe the bug

I guess this is more of a request than a bug report.

@kilfoyle came up with the idea for Expand all | Collapse all buttons to simplify the side navigation. Since all the H1s are expanded, navigating through the website could be overwhelming for users.

Expected behavior

We should provide Expand all | Collapse all buttons in the sidenav so that users can view just the top-level sections or all their children as they wish.

Steps to reproduce

No response

Tooling

• docs-builder
• migration tooling
• I'm not sure