Add EGI branding to the theme about documentation HOT 5 CLOSED

I think this was addressed by PR #244
The list of subsections at the bottom of pages was improved, and by properly using page subtitles these are now a valuable collection of "Next Steps" (true at least for the documentation sections I already revised).

from documentation.

I think this was partially addressed, but the theme definitely need more work.
As an example https://docs.egi.eu/ or https://docs.egi.eu/users/ on the top left the logo is barely readable, things are not really aligned (and docs may also be better replaced by documentation).
We would also benefit from having some more EGI-specific look and feel (whatever it is...)

from documentation.

Some previously collected feedback from communications team:

• Using a picture on the background (see "Communications"->"Photos and Image Database")
• Are you able to adapt it to our style guide, in terms of fonts and colours? (see colours in "Communications"->"EGI Logos")
• Is it possible to remove the 'shadow style' behind the headings?

from documentation.

Is this now resolved?
Where is "Communications"->"Photos and Image Database"?

from documentation.

I don't think the theme is really complete/clean enough.
The location mentioned relate the shared Google Drives. Seems it got moved under 01 Resources - Final.
It's also possible to clean this, and reconsider this task when the guidelines for EGI web sites/services will have been finalised/made available. Should happen in Q1 2023.

from documentation.