[css-align] should be clear from the high-level description whose axis align/justify-self apply to

[dbaron]

I think it should be clearer in the high-level descriptions of the properties, either in the overview or in the definition of align-self and the definition of justify-self, or maybe both, that the block/inline/main/cross axis that these properties care about is the axis of the alignment container, not the axis of the element the properties apply to (which in this case is the alignment subject). I think it would be helpful if that were clear without delving in to the layout-system-specific or value-specific details.