Function justify_self_alignment

fn justify_self_alignment(
    containing_block: &ContainingBlock<'_>,
    free_space: Au,
    justify_self: AlignFlags,
) -> Au

Justifies a block-level box, distributing the free space according to justify-self. Note <center> and <div align> are implemented via internal ‘text-align’ values, which are also handled here. The provided free space should already take margins into account. In particular, it should be zero if there is an auto margin. https://drafts.csswg.org/css-align/#justify-block