Docs: split Tabbed Browser to introduce Dashboard documentation

Describe the solution you'd like

Hi, I was looking for a description of Server sessions in the Dashboard, but was not able to quickly find it. It seems like it's "hidden" in the Tabbed Browser documentation, whose title is not obvious and which has no sections. Long docs like that make it harder to find things.

So this is the way I would improve the docs:

1. Create a new page for the Dashboard, as a copy of Tabbed Browser.
2. Remove content unrelated to the Dashboard (the top paragraph and everything after this: "The Properties tab displays information about the object selected.").
3. Add the "Dashboard" page right after "Tabbed Browser".
4. Add a link to "Dashboard documentation" in the "Tabbed Browser" (for those who have bookmarks). Then remove that section from the "Tabbed Browser" documentation.

I can do a pull request for that if that sounds OK.

Additional context

Also BTW. I would change this:

The Server sessions or Database sessions graph displays the interactions with the server or database.

To add clarification:

The Server sessions or Database sessions graph displays interactions with the server or database. Server sessions are the number of connections to the DBMS, some of which may be idle when connection pooling is enabled in some client applications.

Start with the linked Tabbed Browser documentation and its navigation entry. Create the Dashboard page from the relevant content, place it after Tabbed Browser, add a link for existing bookmarks, remove the moved section, and apply the proposed clarification; done when the pages are separated and navigation is correct.