Add documentation link to logo menu

[castrojo]

https://universal-blue.discourse.group/t/bluefin-docs-should-be-easier-to-get-to/6558

I think putting this in the logomenu makes sense, like this (let's leave the dock for the user's apps):

u
About My System
Documentation
---
App Grid
---
Software Center
System Monitor
Terminal
Containers
Extensions

Repo for this menu is here, probably wouldn't hurt to pull from upstream too:

https://github.com/ublue-os/Logomenu

[castrojo]

Actually this menu needs some work (Who is clicking app grid in here? There's a button on the dock).

u
About My System
Documentation
---
Software Center
---
Extensions
System Monitor
Terminal
---
Containers (only shows up in -dx)

Makes more sense to me, three groups, about your stuff and how to use it, apps, and then the system tools -- tack on the containers when on -dx. That should clean it up. Let's not do the Containers-only-in-dx change until F42 though so we can document the change in the release notes.

[gbrsni]

Maybe it would be neat to also have a system settings entry (if one were to follow MacOS it would be in the same block as the software center but idk about that...).
There would be some redundancy with the fact that on GNOME one can access settings from the top right menu tho, but some people might expect to find them in the logo menu.