Depend the theme, you can have different Docs icons
in the header.
A customization was already possible from the
theme customization file, but now it is as
well possible to override the icon from the theme
itself, making it easier to manage different themes
with different icons.
We change the theme customization variable name
to "icon" instead of "logo", "logo" was already
used for the main logo of the application inside
the theme configuration.
To not create a breaking change, the logo in the
theme customization is now optional, meaning that
if no logo is provided, the default logo will be used.
We add some documentation about this feature.
To have different footer per instance the
content of the footer is now configurable
from the theme customization file.
See THEME_CUSTOMIZATION_FILE_PATH env var.
