feat: revamp the shared navbar

[barjin]

Revamps the shared docs-theme navbar according to the Figma design.

Closes #2678

[apify-service-account]

🗑️ Preview for this PR was deleted.

[barjin]

See https://pr-2679.preview.docs.apify.com/academy for the double navbar

[TC-MO]

Looking good!

Few questions/thoughts/comments

Few things differ slightly from Figma is that on purpose?

• discord icon
• Ask AI button (lack of the icon)

Few thoughts on how it looks

• Discord icon is currently barely visible on dark mode

I see you also already wired top nav to use the specific folders so question whether I should contribute redirects and folder moves that are still necessary work before this ships on top of that PR or should we somehow split it? Let me know which makes more sense, I originally thought that we could split that into two separate PRs

1. Update of the design while keeping the current items in top nav + current behaviour
2. Folder moves & redirects that ship separately.

[barjin]

The rendering discrepancies have been solved in 006d0ab

Regarding the contents of the navbar, I'm fine with either way (even having the new navbar link to the existing docs and fixing the links later on).

Anyway, I just reverted the changes to have the current navbar in the preview. Let me know if you want to merge it like this or make any changes 👍

[TC-MO]

Allright, LGTM, we can merge this revamped navbar today, I'll work on the new items & redirects today so we can double check on Monday and hopefully release. Thanks a lot for this!