HelpHub TOC nested lists styling

[milana_cap]

Issue Description

TOC doesn't reflect parent-child relationship with indentation of child list. Also, alignment is off.

Context

This is possibly caused by overriding old theme (we already had issue with title font size being too large).

Expected Result:

Style should match TOC found here: ​https://developer.wordpress.org/themes/functionality/administration-menus/.

Screenshot:

Actual Result:

This is how it looks now: ​https://wordpress.org/support/article/first-steps-with-wordpress-b/

Screenshot:

[coffee2code]

In 9492:

Support Hub, ToC: Fix so markup for ToC subitems are nested under parent items instead of being their peer.

Props milana_cap.
See #4692.

[coffee2code]

In 9493:

Support Hub, ToC: Improve ToC styling.

Improves overall alignment and styling of list subitems.

Props milana_cap.
Fixes #4692.