To add properties to the outer block of a graphical admonition.
These properties are added to the outer block containing the
entire graphical admonition, including its title.
It is used when the parameter
admon.graphics is set to nonzero.
Use this attribute-set to set the space above and below,
and any indent for the whole admonition.
In addition to these properties, a graphical admonition
also applies the admonition.title.properties
attribute-set to the title, and applies the
to the rest of the content.