doc: highlight pointed column in NIC overview table

doc: highlight pointed column in NIC overview table

Every cells of a driver column are painted in yellow.

The trick is to generate some empty content as a big column
above and below the pointed cell.

The position: relative attribute is used for the highlight position
but it makes the border to disappear.

The overflow: hidden attribute is used to mask the generated content
outside of the table.

The class .wy-nav-content has a background which masks the highlighting.
Setting an opacity lower than 1, creates a new stack context and let
the column highlight to be shown.

The background of odd rows was grey and opaque. It is redefined with
a transparent alpha ratio in order to see highlighting on such rows.

Signed-off-by: Thomas Monjalon <thomas.monjalon@6wind.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: John McNamara <john.mcnamara@intel.com>