Add top level menu to the platform docs

[mtrunkat]

The menu should contain:

Introduction Actors Proxy Storage Integrations Monitoring Collaboration

• Schedules will go to actors as they are not so important and do not contain nested pages
• Access rights and Organizations will be in collaboration

I am adding #509 as a blocker. I'd first restructure everything in the current tree structure. We will see what it will look like. There will be fewer pages than we have now. And based on that we will decide if we proceed with this.

@B4nan so let's wait with this, I marking it as a low prio

[B4nan]

cc @barjin, we will need to adjust the second level navigation implementation to accommodate this, currently you can only set it per docusaurus instance, and we will need to make it more granular, and support variants - platform will have its own, not sure if academy too? but it will need to be restricted to some URL prefix.

[barjin]

What's the status on this? The blocking issue seems to be done + I have done this for the academy section already, so it's only a matter of whether we still want this - and what the categories should be.

[mtrunkat]

Let's wait with this. We are still rewriting the content, and after that, we will get back to the structure and menu. Thanks!