fix: order for list pages + navbar improv

[JTorreG]

Proposed changes

Imports the list-main.html changes from the docs repo to the theme

• This change makes items in the list pages appear in the same order as they appear in the side navigation

Improves the navigation bar:

• When browsing a section list-page the navigation will highlight the section and (new) expand it to show the same subsections as the list page is showing:

before:

after:

Closes DOC-146

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• I have updated any relevant documentation (README.md and CHANGELOG.md)

[ADubhlaoich]

LGTM! Great UX improvements.