feat(linux): improve Support tab

> Comparing with the info on the Keyman for Windows diagnostic report:
> https://help.keyman.com/knowledge-base/?id=40
>
> Should we have a similar layout of the support tab across the products?
> 1. e.g. the center panel displays the Keyman logo, Keyman for Linux version? (without having to generate report to see it) and a link to the community site forum
>
> 2. Right panel having "Useful Links" to
> * keyman.com
> * "Diagnostics" which could then make use of the buttons you've made.
> * Online help ([help.keyman.com](https://help.keyman.com/products/linux/18.0/)

_Originally posted by @darcywong00 in [#15576](https://github.com/keymanapp/keyman/pull/15576/changes#r2856663284)_